U.S. patent application number 16/944665 was filed with the patent office on 2021-02-11 for systems and methods for bleeder control related to triac dimmers associated with led lighting.
The applicant listed for this patent is ON-BRIGHT ELECTRONICS (SHANGHAI) CO., LTD.. Invention is credited to JUN ZHOU, LIQIANG ZHU.
Application Number | 20210045213 16/944665 |
Document ID | / |
Family ID | 1000005077798 |
Filed Date | 2021-02-11 |
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United States Patent
Application |
20210045213 |
Kind Code |
A1 |
ZHU; LIQIANG ; et
al. |
February 11, 2021 |
SYSTEMS AND METHODS FOR BLEEDER CONTROL RELATED TO TRIAC DIMMERS
ASSOCIATED WITH LED LIGHTING
Abstract
System and method for controlling one or more light emitting
diodes. For example, the system includes: a current regulator
including a first regulator terminal and a second regulator
terminal, the first regulator terminal being configured to receive
a diode current flowing through the one or more light emitting
diodes, the current regulator being configured to generate a
sensing signal representing the diode current, the second regulator
terminal being configured to output the sensing signal; a bleeder
controller including a first controller terminal and a second
controller terminal, the first controller terminal being configured
to receive the sensing signal from the second regulator terminal,
the bleeder controller being configured to generate a first bleeder
control signal based at least in part on the sensing signal, the
second controller terminal being configured to output the first
bleeder control signal.
Inventors: |
ZHU; LIQIANG; (Shanghai,
CN) ; ZHOU; JUN; (Shanghai, CN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ON-BRIGHT ELECTRONICS (SHANGHAI) CO., LTD. |
Shanghai |
|
CN |
|
|
Family ID: |
1000005077798 |
Appl. No.: |
16/944665 |
Filed: |
July 31, 2020 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H05B 45/397 20200101;
H05B 45/3575 20200101 |
International
Class: |
H05B 45/397 20060101
H05B045/397; H05B 45/3575 20060101 H05B045/3575 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 6, 2019 |
CN |
201910719931.X |
Claims
1. A system for controlling one or more light emitting diodes, the
system comprising: a current regulator including a first regulator
terminal and a second regulator terminal, the first regulator
terminal being configured to receive a diode current flowing
through the one or more light emitting diodes, the current
regulator being configured to generate a sensing signal
representing the diode current, the second regulator terminal being
configured to output the sensing signal; a bleeder controller
including a first controller terminal and a second controller
terminal, the first controller terminal being configured to receive
the sensing signal from the second regulator terminal, the bleeder
controller being configured to generate a first bleeder control
signal based at least in part on the sensing signal, the second
controller terminal being configured to output the first bleeder
control signal, the first bleeder control signal indicating whether
a bleeder current is allowed or not allowed to be generated; and a
bleeder including a first bleeder terminal and a second bleeder
terminal, the first bleeder terminal being configured to receive
the first bleeder control signal from the second controller
terminal, the second bleeder terminal being configured to receive a
rectified voltage associated with a TRIAC dimmer and generated by a
rectifying bridge; wherein: the bleeder includes a current
controller and a current generator; the current controller is
configured to receive the first bleeder control signal and generate
an input voltage based at least in part on the first bleeder
control signal; and the current generator is configured to receive
the rectified voltage and the input voltage and generate the
bleeder current based at least in part on the input voltage;
wherein, if the first bleeder control signal indicates that the
bleeder current is not allowed to be generated: the current
controller is configured to gradually reduce the input voltage from
a first voltage magnitude at a first time to a second voltage
magnitude at a second time; and the current generator is configured
to gradually reduce the bleeder current from a first current
magnitude at the first time to a second current magnitude at the
second time; wherein the second time follows the first time by a
predetermined duration of time.
2. The system of claim 1 wherein: the current controller includes a
switch, an amplifier, a resistor, and a capacitor; wherein: the
capacitor includes a first capacitor terminal and a second
capacitor terminal, the first capacitor terminal being configured
to provide the input voltage, the second capacitor terminal being
biased to a ground voltage; the resistor includes a first resistor
terminal and a second resistor terminal, the second resistor
terminal being biased to the ground voltage; and the amplifier
includes a first amplifier input terminal, a second amplifier input
terminal, and an amplifier output terminal, the second amplifier
input terminal being connected to the amplifier output terminal,
the first amplifier input terminal being biased to a reference
voltage; wherein: the switch is configured to: receive the first
bleeder control signal; and based at least in part on the first
bleeder control signal, connect the first capacitor terminal to the
amplifier output terminal or to the first resistor terminal; and
the switch is further configured to: if the bleeder current is
allowed to be generated, connect the first capacitor terminal to
the amplifier output terminal to generate the bleeder current based
at least in part on the reference voltage; and if the bleeder
current is not allowed to be generated, connect the first capacitor
terminal to the first resistor terminal to gradually reduce the
bleeder current from the first current magnitude at the first time
to the second current magnitude at the second time.
3. The system of claim 1 wherein: the bleeder controller includes a
comparator and a first delayed-signal generator; wherein: the
comparator is configured to receive the sensing signal and a
threshold voltage and generate a comparison signal based at least
in part on the sensing signal and the threshold voltage; and the
first delayed-signal generator is configured to receive the
comparison signal and generate the first bleeder control signal
based at least in part on the comparison signal; wherein the first
delayed-signal generator is further configured to, if the
comparison signal indicates that the sensing signal becomes larger
than the threshold voltage, change the first bleeder control signal
from a first logic level to a second logic level after a first
predetermined delay, the first predetermined delay being larger
than zero in magnitude; wherein: the first logic level indicates
that the bleeder current is allowed to be generated; and the second
logic level indicates that the bleeder current is not allowed to be
generated.
4. The system of claim 3 wherein: the bleeder controller is further
configured to generate N bleeder control signals corresponding to N
predetermined delays respectively, N being an integer larger than
1; wherein: the N bleeder control signals include a 1.sup.st
bleeder control signal, . . . , an n.sup.th bleeder control signal,
. . . , and an N.sup.th bleeder control signal, n being an integer
larger than 1 but smaller than N; and the N predetermined delays
include a 1.sup.st predetermined delay, . . . , an n.sup.th
predetermined delay, . . . , and an N.sup.th predetermined delay;
wherein: the 1.sup.st bleeder control signal is the first bleeder
control signal; the 1.sup.st predetermined delay is the first
predetermined delay; and each delay of the N predetermined delays
is larger than zero in magnitude; wherein the bleeder controller is
further configured to: if the (n-1).sup.th bleeder control signal
changes from indicating that the bleeder current is allowed to be
generated to indicating that the bleeder current is not allowed to
be generated, change the n.sup.th bleeder control signal after the
n.sup.th predetermined delay; and if the (N-1).sup.th bleeder
control signal changes from indicating that the bleeder current is
allowed to be generated to indicating that the bleeder current is
not allowed to be generated, change the N.sup.th bleeder control
signal after the N.sup.th predetermined delay.
5. The system of claim 4 wherein: the current controller includes N
switches, N amplifiers, a resistor, and a capacitor, the N switches
and the N amplifiers corresponding to N reference voltages; the N
switches include a 1.sup.st switch, . . . , an n.sup.th switch, . .
. , and an N.sup.th switch; the N amplifiers include a 1.sup.st
amplifier, . . . , an n.sup.th amplifier, . . . , and an N.sup.th
amplifier; and the N reference voltages include a 1.sup.st
reference voltage, . . . , an n.sup.th reference voltage, . . . ,
and an N.sup.th reference voltage; wherein: the 1.sup.st amplifier
includes a 1.sup.st amplifier positive input amplifier, a 1.sup.st
amplifier negative input terminal, and a 1.sup.st amplifier output
terminal, the 1.sup.st amplifier negative input terminal being
connected to the 1.sup.st amplifier output terminal, the 1.sup.st
amplifier positive input amplifier being biased to the 1.sup.st
reference voltage; the n.sup.th amplifier includes an n.sup.th
amplifier positive input terminal, an n.sup.th amplifier negative
input terminal, and an n.sup.th amplifier output terminal, the
n.sup.th amplifier negative input terminal being connected to the
n.sup.th amplifier output terminal; and the N.sup.th amplifier
includes an N.sup.th amplifier positive input terminal, an N.sup.th
amplifier negative input terminal, and an N.sup.th amplifier output
terminal, the N.sup.th amplifier negative input terminal being
connected to the N.sup.th amplifier output terminal; wherein: the
capacitor includes a first capacitor terminal and a second
capacitor terminal, the first capacitor terminal being configured
to provide the input voltage, the second capacitor terminal being
biased to a ground voltage; and the resistor includes a first
resistor terminal and a second resistor terminal, the second
resistor terminal being connected to the 2.sup.nd amplifier output
terminal; wherein the 1.sup.st switch is configured to: receive the
1.sup.st bleeder control signal; and based at least in part on the
1.sup.st bleeder control signal, connect the first capacitor
terminal to the 1.sup.st amplifier output terminal or to the first
resistor terminal; wherein the 1.sup.st switch is further
configured to: if the 1.sup.st bleeder control signal indicates
that the bleeder current is allowed to be generated, connect the
first capacitor terminal to the 1.sup.st amplifier output terminal;
and if the 1.sup.st bleeder control signal indicates that the
bleeder current is not allowed to be generated, connect the first
capacitor terminal to the first resistor terminal so that the first
capacitor terminal is connected to the 2.sup.nd amplifier output
terminal through the resistor; wherein the n.sup.th switch is
configured to: receive the n.sup.th bleeder control signal; and
based at least in part on the n.sup.th bleeder control signal,
connect the n.sup.th amplifier positive input terminal to the
n.sup.th reference voltage or to the (n+1).sup.th amplifier output
terminal; wherein the n.sup.th switch is further configured to: if
the n.sup.th bleeder control signal indicates that the bleeder
current is allowed to be generated, connect the n.sup.th amplifier
positive input terminal to the n.sup.th reference voltage; and if
the n.sup.th bleeder control signal indicates that the bleeder
current is not allowed to be generated, connect the n.sup.th
amplifier positive input terminal to the (n+1).sup.th amplifier
output terminal; wherein the N.sup.th switch is configured to:
receive the N.sup.th bleeder control signal; and based at least in
part on the N.sup.th bleeder control signal, connect the N.sup.th
amplifier positive input terminal to the N.sup.th reference voltage
or to the ground voltage; wherein the N.sup.th switch is further
configured to: if the N.sup.th bleeder control signal indicates
that the bleeder current is allowed to be generated, connect the
N.sup.th amplifier positive input terminal to the N.sup.th
reference voltage; and if the N.sup.th bleeder control signal
indicates that bleeder current is not allowed to be generated,
connect the N.sup.th amplifier positive input terminal to the
ground voltage; wherein: the (n-1).sup.th reference voltage is
larger than the n.sup.th reference voltage; the n.sup.th reference
voltage is larger than the (n+1).sup.th reference voltage; and the
N.sup.th reference voltage is larger than zero.
6. The system of claim 4 wherein: the bleeder controller further
includes N delayed-signal generators, the N delayed-signal
generators corresponding to the N predetermined delays; and the N
delayed-signal generators include a 1.sup.st delayed-signal
generator, . . . , an n.sup.th delayed-signal generator, . . . ,
and an N.sup.th delayed-signal generator, the 1.sup.st
delayed-signal generator being the first delayed-signal generator;
wherein the first delayed-signal generator is further configured
to, if the comparison signal indicates that the sensing signal
becomes larger than the threshold voltage, change the first bleeder
control signal after the first predetermined delay; wherein the
n.sup.th delayed-signal generator is configured to: receive the
(n-1).sup.th bleeder control signal; generate the n.sup.th bleeder
control signal based at least in part on the (n-1).sup.th bleeder
control signal; and if the (n-1).sup.th bleeder control signal
indicates that the sensing signal becomes larger than the threshold
voltage, change the n.sup.th bleeder control signal after the
n.sup.th predetermined delay; wherein the N.sup.th delayed-signal
generator is configured to: receive the (N-1).sup.th bleeder
control signal; generate the N.sup.th bleeder control signal based
at least in part on the (N-1).sup.th bleeder control signal; and if
the (N-1).sup.th bleeder control signal indicates that the sensing
signal becomes larger than the threshold voltage, change the
N.sup.th bleeder control signal after the N.sup.th predetermined
delay.
7. The system of claim 1 wherein: the current regulator includes an
amplifier, a transistor, and a resistor; the transistor includes a
gate terminal, a drain terminal, and a source terminal; the
amplifier includes an amplifier positive input terminal, an
amplifier negative input terminal, and an amplifier output
terminal; and the resistor includes a first resistor terminal and a
second resistor terminal: wherein: the gate terminal is coupled to
the amplifier output terminal; the drain terminal is coupled to the
one or more light emitting diodes; the source terminal is coupled
to the first resistor terminal; the amplifier positive input
terminal is biased to a reference voltage; the amplifier negative
input terminal is coupled to the source terminal; and the second
resistor terminal is biased to a ground voltage; wherein the first
resistor terminal is configured to generate the sensing signal
representing the diode current flowing through the one or more
light emitting diodes.
8. The system of claim 1 wherein: the current generator includes an
amplifier, a transistor, and a resistor; the transistor includes a
gate terminal, a drain terminal, and a source terminal; the
amplifier includes an amplifier positive input terminal, an
amplifier negative input terminal, and an amplifier output
terminal; and the resistor includes a first resistor terminal and a
second resistor terminal; wherein: the gate terminal is coupled to
the amplifier output terminal; the drain terminal is biased to the
rectified voltage associated with the TRIAC dimmer and generated by
the rectifying bridge; the source terminal is coupled to the first
resistor terminal; the second resistor terminal is biased to a
ground voltage; the amplifier negative input terminal is coupled to
the source terminal; and the amplifier positive input terminal is
configured to receive the input voltage.
9. A system for controlling one or more light emitting diodes, the
system comprising: a current regulator including a first regulator
terminal and a second regulator terminal, the first regulator
terminal being configured to receive a diode current flowing
through the one or more light emitting diodes, the current
regulator being configured to generate a sensing signal
representing the diode current, the second regulator terminal being
configured to output the sensing signal; a voltage divider
including a first divider terminal and a second divider terminal,
the first divider terminal being configured to receive a rectified
voltage associated with a TRIAC dimmer and generated by a
rectifying bridge, the voltage divider being configured to generate
a converted voltage proportional to the rectified voltage, the
second divider terminal being configured to output the converted
voltage; a bleeder controller including a first controller
terminal, a second controller terminal and a third controller
terminal, the first controller terminal being configured to receive
the converted voltage from the second divider terminal, the second
controller terminal being configured to receive the sensing signal
from the second regulator terminal, the bleeder controller being
configured to generate a first bleeder control signal based at
least in part on the converted voltage, the third controller
terminal being configured to output the first bleeder control
signal, the first bleeder control signal indicating whether a
bleeder current is allowed or not allowed to be generated; and a
bleeder including a first bleeder terminal and a second bleeder
terminal, the first bleeder terminal being configured to receive
the first bleeder control signal from the third controller
terminal, the second bleeder terminal being configured to receive
the rectified voltage; wherein: the bleeder includes a current
controller and a current generator; the current controller is
configured to receive the first bleeder control signal and generate
an input voltage based at least in part on the first bleeder
control signal; and the current generator is configured to receive
the rectified voltage and the input voltage and generate the
bleeder current based at least in part on the input voltage;
wherein, if the first bleeder control signal indicates that the
bleeder current is not allowed to be generated: the current
controller is configured to gradually reduce the input voltage from
a first voltage magnitude at a first time to a second voltage
magnitude at a second time; and the current generator is configured
to gradually reduce the bleeder current from a first current
magnitude at the first time to a second current magnitude at the
second time; wherein the second time follows the first time by a
predetermined duration of time.
10. The system of claim 9 wherein: the bleeder controller includes
a conduction phase detector configured to: determine a phase range
within which the TRIAC dimmer is in a conduction state based on at
least information associated with the converted voltage; and
generate a detection signal by comparing the phase range within
which the TRIAC dimmer is in the conduction state and a
predetermined conduction phase threshold; and the bleeder
controller is further configured to: if the phase range within
which the TRIAC dimmer is in the conduction state is determined to
be larger than the predetermined conduction phase threshold,
generate the first bleeder control signal based at least in part on
the sensing signal; and if the phase range within which the TRIAC
dimmer is in the conduction state is determined to be smaller than
the predetermined conduction phase threshold, generate the first
bleeder control signal based at least in part on the converted
voltage.
11. The system of claim 10 wherein: the bleeder controller further
includes a first comparator, a second comparator, a switch, and a
first delayed-signal generator; wherein: the first comparator is
configured to receive the converted voltage and a first threshold
voltage and generate a first comparison signal based at least in
part on the converted voltage and the first threshold voltage; and
the second comparator is configured to receive the sensing signal
and a second threshold voltage and generate a second comparison
signal based at least in part on the sensing signal and the second
threshold voltage; wherein the conduction phase detector is further
configured to: receive the first comparison signal; and generate
the detection signal based at least in part on the first comparison
signal; wherein the switch is configured to receive the detection
signal; wherein, if the phase range within which the TRIAC dimmer
is in the conduction state is determined to be smaller than the
predetermined conduction phase threshold: the switch is configured
to output the first comparison signal to the first delayed-signal
generator; and if the first comparison signal indicates that the
converted voltage becomes larger than the first threshold voltage,
change the first bleeder control signal from a first logic level to
a second logic level after a first predetermined delay; wherein, if
the phase range within which the TRIAC dimmer is in the conduction
state is determined to be larger than the predetermined conduction
phase threshold: the switch is configured to output the second
comparison signal to the first delayed-signal generator; and if the
second comparison signal indicates that the sensing signal becomes
larger than the second threshold voltage, change the first bleeder
control signal from the first logic level to the second logic level
after the first predetermined delay; wherein: the first
predetermined delay is larger than zero in magnitude; the first
logic level indicates that the bleeder current is allowed to be
generated; and the second logic level indicates that the bleeder
current is not allowed to be generated.
12. The system of claim 11 wherein: the conduction phase detector
includes a duration determination device and a phase detection
device; wherein: the duration determination device is configured to
receive the first comparison signal, determine a time duration
during which the first comparison signal indicates the converted
voltage is smaller than the first threshold voltage, and output a
timing signal representing the time duration; and the phase
detection device is configured to receive the timing signal
representing the time duration, compare the time duration and a
duration threshold, and generate the detection signal based at
least in part on the time duration and the duration threshold, the
detection signal indicating whether the time duration is larger
than the duration threshold; wherein: if the detection signal
indicates that the time duration is larger than the duration
threshold, the phase range within which the TRIAC dimmer is in the
conduction state is determined to be smaller than the predetermined
conduction phase threshold; and if the detection signal indicates
that the time duration is smaller than the duration threshold, the
phase range within which the TRIAC dimmer is in the conduction
state is determined to be larger than the predetermined conduction
phase threshold.
13. The system of claim 11 wherein: the bleeder controller is
configured to generate N bleeder control signals corresponding to N
predetermined delays respectively, N being an integer larger than
1; wherein: the N bleeder control signals include a 1.sup.st
bleeder control signal, . . . , an n.sup.th bleeder control signal,
. . . , and an N.sup.th bleeder control signal, n being an integer
larger than 1 but smaller than N; and the N predetermined delays
include a 1.sup.st predetermined delay, . . . , an n.sup.th
predetermined delay, . . . , and an N.sup.th predetermined delay,
each predetermined delay of the N predetermined delays being larger
than zero in magnitude; wherein: the 1.sup.st bleeder control
signal is the first bleeder control signal; and the 1.sup.st
predetermined delay is the first predetermined delay; wherein the
bleeder controller is further configured to: if the (n-1).sup.th
bleeder control signal changes from indicating that the bleeder
current is allowed to be generated to indicating that the bleeder
current is not allowed to be generated, change the n.sup.th bleeder
control signal after the n.sup.th predetermined delay; and if the
(N-1).sup.th bleeder control signal changes from indicating that
the bleeder current is allowed to be generated to indicating that
the bleeder current is not allowed to be generated, change the
N.sup.th bleeder control signal after the N.sup.th predetermined
delay.
14. The system of claim 13 wherein: the bleeder controller further
includes N delayed-signal generators; and the N delayed-signal
generators include a 1.sup.st delayed-signal generator, . . . , an
n.sup.th delayed-signal generator, . . . , and an N.sup.th
delayed-signal generator; wherein the 1.sup.st delayed-signal
generator is the first delayed-signal generator.
15. A system for controlling one or more light emitting diodes, the
system comprising: a current regulator including a first regulator
terminal and a second regulator terminal, the first regulator
terminal being configured to receive a diode current flowing
through the one or more light emitting diodes, the current
regulator being configured to generate a sensing signal
representing the diode current, the second regulator terminal being
configured to output the sensing signal; a voltage divider
including a first divider terminal and a second divider terminal,
the first divider terminal being configured to receive a rectified
voltage associated with a TRIAC dimmer and generated by a
rectifying bridge, the voltage divider being configured to generate
a converted voltage proportional to the rectified voltage, the
second divider terminal being configured to output the converted
voltage; a bleeder controller including a first controller
terminal, a second controller terminal and a third controller
terminal, the first controller terminal being configured to receive
the converted voltage from the second divider terminal, the second
controller terminal being configured to receive the sensing signal
from the second regulator terminal, the bleeder controller being
configured to generate a first bleeder control signal based at
least in part on the converted voltage, the third controller
terminal being configured to output the first bleeder control
signal, the first bleeder control signal indicating whether a
bleeder current is allowed or not allowed to be generated; and a
bleeder including a first bleeder terminal and a second bleeder
terminal, the first bleeder terminal being configured to receive
the first bleeder control signal from the third controller
terminal, the second bleeder terminal being configured to receive
the rectified voltage, the bleeder being configured to generate the
bleeder current based at least in part on the first bleeder control
signal; wherein the bleeder controller is configured to: determine
a phase range within which the TRIAC dimmer is in a conduction
state based on at least information associated with the converted
voltage; and generate a detection signal by comparing a
predetermined conduction phase threshold and the phase range within
which the TRIAC dimmer is in the conduction state; wherein the
bleeder controller is further configured to: if the detection
signal indicates that the phase range within which the TRIAC dimmer
is in the conduction state is larger than the predetermined
conduction phase threshold, generate the first bleeder control
signal based at least in part on the sensing signal; and if the
detection signal indicates that the phase range within which the
TRIAC dimmer is in the conduction state is determined to be smaller
than the predetermined conduction phase threshold, generate the
first bleeder control signal based at least in part on the
converted voltage; wherein: if the first bleeder control signal
indicates that the bleeder current is not allowed to be generated,
the current generator is configured to gradually reduce the bleeder
current from a first current magnitude at a first time to a second
current magnitude at a second time; wherein the second time follows
the first time by a predetermined duration of time.
16. The system of claim 15 wherein: the bleeder controller further
includes a delayed-signal generator; wherein: the delayed-signal
generator is configured to change the first bleeder control signal
from a first logic level to a second logic level after a
predetermined delay, the predetermined delay being larger than zero
in magnitude; the first logic level indicates that the bleeder
current is allowed to be generated; and the second logic level
indicates that the bleeder current is not allowed to be
generated.
17. The system of claim 15 wherein: the bleeder controller further
includes N delayed-signal generators, the N delayed-signal
generators being configured to generate N bleeder control signals
corresponding to N predetermined delays respectively, N being an
integer larger than 1; and the bleeder is configured to receive the
N bleeder control signals; wherein: the N delayed-signal generators
include a 1.sup.st delayed-signal generator, . . . , an n.sup.th
delayed-signal generator, . . . , and an Nth delayed-signal
generator, n being an integer larger than 1 but smaller than N; the
N bleeder control signals include a 1.sup.st bleeder control
signal, . . . , an n.sup.th bleeder control signal, . . . , and an
N.sup.th bleeder control signal, the 1.sup.st bleeder control
signal being the first bleeder control signal; and the N
predetermined delays include a 1.sup.st predetermined delay, . . .
, an n.sup.th predetermined delay, . . . , and an N.sup.th
predetermined delay, each predetermined delay of the N
predetermined delays being larger than zero in magnitude; wherein
the n.sup.th delayed-signal generator is configured to receive the
(n-1).sup.th bleeder control signal and change the n.sup.th bleeder
control signal after the n.sup.th predetermined delay if the
(n-1).sup.th bleeder control signal indicates a change from the
bleeder current being allowed to be generated to the bleeder
current not being allowed to be generated; wherein, the bleeder is
further configured to, if the bleeder current changes from being
allowed to be generated to not being allowed to be generated,
reduce the bleeder current from a 1.sup.st predetermined magnitude
to a 2.sup.nd predetermined magnitude during a predetermined
duration of time in response to at least a change of the 1.sup.st
bleeder control signal; reduce the bleeder current from an n.sup.th
predetermined magnitude to an (n+1).sup.th predetermined magnitude
during the predetermined duration of time in response to at least a
change of the n.sup.th bleeder control signal; and reduce the
bleeder current from an N.sup.th predetermined magnitude to zero
during the predetermined duration of time in response to at least a
change of the N.sup.th bleeder control signal; wherein: the
(n-1).sup.th predetermined magnitude is larger than the n.sup.th
predetermined magnitude; the n.sup.th predetermined magnitude is
larger than the (n+1).sup.th predetermined magnitude; and the
N.sup.th predetermined magnitude is larger than zero.
18. A method for controlling one or more light emitting diodes, the
method comprising: receiving a diode current flowing through the
one or more light emitting diodes; generating a sensing signal
representing the diode current; outputting the sensing signal;
receiving the sensing signal; generating a first bleeder control
signal based at least in part on the sensing signal, the first
bleeder control signal indicating whether a bleeder current is
allowed or not allowed to be generated; outputting the first
bleeder control signal; receiving the first bleeder control signal;
generating an input voltage based at least in part on the first
bleeder control signal; receiving the input voltage and a rectified
voltage associated with a TRIAC dimmer; generating the bleeder
current based at least in part on the input voltage; wherein: the
generating an input voltage based at least in part on the first
bleeder control signal includes, if the first bleeder control
signal indicates that the bleeder current is not allowed to be
generated, gradually reducing the input voltage from a first
voltage magnitude at a first time to a second voltage magnitude at
a second time; and the generating the bleeder current based at
least in part on the input voltage includes, if the first bleeder
control signal indicates that the bleeder current is not allowed to
be generated, gradually reducing the bleeder current from a first
current magnitude at the first time to a second current magnitude
at the second time; wherein the second time follows the first time
by a predetermined duration of time.
19. A method for controlling one or more light emitting diodes, the
method comprising: receiving a diode current flowing through the
one or more light emitting diodes; generating a sensing signal
representing the diode current; outputting the sensing signal;
receiving a rectified voltage associated with a TRIAC dimmer;
generating a converted voltage proportional to the rectified
voltage; outputting the converted voltage; receiving the converted
voltage and the sensing signal; generating a first bleeder control
signal based at least in part on the converted voltage, the first
bleeder control signal indicating whether a bleeder current is
allowed or not allowed to be generated; outputting the first
bleeder control signal; receiving the first bleeder control signal;
generating an input voltage based at least in part on the first
bleeder control signal; receiving the input voltage and the
rectified voltage; and generating the bleeder current based at
least in part on the input voltage; wherein: the generating an
input voltage based at least in part on the first bleeder control
signal includes, if the first bleeder control signal indicates that
the bleeder current is not allowed to be generated, gradually
reducing the input voltage from a first voltage magnitude at a
first time to a second voltage magnitude at a second time; and the
generating the bleeder current based at least in part on the input
voltage includes, if the first bleeder control signal indicates
that the bleeder current is not allowed to be generated, gradually
reducing the bleeder current from a first current magnitude at the
first time to a second current magnitude at the second time;
wherein the second time follows the first time by a predetermined
duration of time.
20. A method for controlling one or more light emitting diodes, the
method comprising: receiving a diode current flowing through the
one or more light emitting diodes; generating a sensing signal
representing the diode current; outputting the sensing signal;
receiving a rectified voltage associated with a TRIAC dimmer;
generating a converted voltage proportional to the rectified
voltage; outputting the converted voltage; receive the converted
voltage and the sensing signal; generating a first bleeder control
signal based at least in part on the converted voltage, the first
bleeder control signal indicating whether a bleeder current is
allowed or not allowed to be generated; outputting the first
bleeder control signal; receiving the first bleeder control signal
and the rectified voltage; and generating the bleeder current based
at least in part on the input voltage; wherein the generating a
first bleeder control signal based at least in part on the
converted voltage includes: determining a phase range within which
the TRIAC dimmer is in a conduction state based on at least
information associated with the converted voltage; generating a
detection signal by comparing a predetermined conduction phase
threshold and the phase range within which the TRIAC dimmer is in
the conduction state; if the detection signal indicates that the
phase range within which the TRIAC dimmer is in the conduction
state is larger than the predetermined conduction phase threshold,
generating the first bleeder control signal based at least in part
on the sensing signal; and if the detection signal indicates that
the phase range within which the TRIAC dimmer is in the conduction
state is smaller than the predetermined conduction phase threshold,
generating the first bleeder control signal based at least in part
on the converted voltage; wherein the generating the bleeder
current based at least in part on the input voltage includes, if
the first bleeder control signal indicates that the bleeder current
is not allowed to be generated, gradually reducing the bleeder
current from a first current magnitude at a first time to a second
current magnitude at a second time; wherein the second time follows
the first time by a predetermined duration of time.
Description
1. CROSS-REFERENCES TO RELATED APPLICATIONS
[0001] This application claims priority to Chinese Patent
Application No. 201910719931.X, filed Aug. 6, 2019, incorporated by
reference herein for all purposes.
2. BACKGROUND OF THE INVENTION
[0002] Certain embodiments of the present invention are directed to
circuits. More particularly, some embodiments of the invention
provide systems and methods for bleeder control related to Triode
for Alternating Current (TRIAC) dimmers. Merely by way of example,
some embodiments of the invention have been applied to light
emitting diodes (LEDs). But it would be recognized that the
invention has a much broader range of applicability.
[0003] With development in the light-emitting diode (LED) lighting
market, many LED manufacturers have placed LED lighting products at
an important position in market development. LED lighting products
often need dimmer technology to provide consumers with a unique
visual experience. Since Triode for Alternating Current (TRIAC)
dimmers have been widely used in conventional lighting systems such
as incandescent lighting systems, the TRIAC dimmers are also
increasingly being used in LED lighting systems.
[0004] Conventionally, the TRIAC dimmers usually are designed
primarily for incandescent lights with pure resistive loads and low
luminous efficiency. Such characteristics of incandescent lights
often help to meet the requirements of TRIAC dimmers in holding
currents. Therefore, the TRIAC dimmers usually are suitable for
light dimming when used with incandescent lights.
[0005] However, when the TRIAC dimmers are used with more efficient
LEDs, it is often difficult to meet the requirements of TRIAC
dimmers in holding currents due to the reduced input power needed
to achieve equivalent illumination to that of incandescent lights.
Therefore, conventional LED lighting systems often utilize bleeder
units to provide compensation in order to satisfy the requirements
of TRIAC dimmers in holding currents.
[0006] FIG. 1 is a simplified diagram showing a conventional LED
lighting system using a TRIAC dimmer. As shown in FIG. 1, the main
control unit of the LED lighting system 100 includes a constant
current unit 110 (e.g., a current regulator), a bleeder unit 120,
and a bleeder control unit 130. The bleeder unit 120 includes an
amplifier 122, a transistor 124, a resistor 126, and a switch 128.
A bleeder current 190 is determined by the resistance value of the
resistor 126 and the reference voltage 192 received by the
amplifier 122. For example, if the transistor 124 is in the
saturation region, the bleeder current 190 is determined as
follows:
I bleed = V ref R ( Equation 1 ) ##EQU00001##
[0007] where I.sub.bleed represents the bleeder current 190,
V.sub.ref represents the reference voltage 192, and R represents
the resistance value of the resistor 126.
[0008] The bleeder control unit 130 is configured to detect the
change of an LED current 194 that flows through one or more LEDs
140. If the LED current 194 is relatively high, the bleeder control
unit 130 does not allow the bleeder unit 120 to generate the
bleeder current 190 according to Equation 1, such as by closing the
switch 128 and thus biasing the gate terminal of the transistor 124
to the ground. If the LED current 194 is relatively low, the
bleeder control unit 130 allows the bleeder unit 120 to generate
the bleeder current 190 according to Equation 1, so that a TRIAC
dimmer 150 can operate normally.
[0009] FIG. 2 shows simplified timing diagrams for the conventional
LED lighting system using the TRIAC dimmer as shown in FIG. 1. The
waveform 298 represents a rectified voltage 198 (e.g., VIN) as a
function of time, the waveform 294 represents the LED current 194
(e.g., I.sub.LED) as a function of time, the waveform 296
represents a control signal 196 that is used to control the switch
128 (e.g., SW1), and the waveform 290 represents the bleeder
current 190 (e.g., I.sub.bleed).
[0010] When the LED lighting system 100 works properly, the TRIAC
dimmer 150 clips parts of a waveform for an AC input voltage 180
(e.g., VAC). From time to to time ti, the rectified voltage 198
(e.g., VIN) is at a voltage level that is close or equal to zero
volts as shown by the waveform 298, the LED current 194 (e.g.,
I.sub.LED) is equal to zero in magnitude as shown by the waveform
294, the control signal 196 is at a logic low level in order to
open the switch 128 (e.g., SW1) as shown by the waveform 296, and
the bleeder current 190 is allowed to be generated as shown by the
waveform 290. As an example, from time to to time ti, the bleeder
current 190 is allowed to be generated as shown by the waveform
290, so the bleeder current 190 remains at zero and then increases
in magnitude as shown by the waveform 290. From time t.sub.1 to
time t.sub.2, the rectified voltage 198 (e.g., VIN) is at a high
voltage level (e.g., a high voltage level that is not constant) as
shown by the waveform 298, the LED current 194 (e.g., I.sub.LED) is
at a high current level as shown by the waveform 294, the control
signal 196 is at a logic high level in order to close the switch
128 (e.g., SW1) as shown by the waveform 296, and the bleeder
current 190 is not allowed to be generated as shown by the waveform
290. As an example, from time t.sub.1to time t.sub.2, the bleeder
current 190 drops to zero and then remains at zero in
magnitude.
[0011] From time t.sub.2 to time t.sub.3, the rectified voltage 198
(e.g., VIN) changes from the high voltage level to a low voltage
level (e.g., a low voltage level that is not constant but larger
than zero volts) as shown by the waveform 298, the LED current 194
(e.g., I.sub.LED) is at the low current level as shown by the
waveform 294, the control signal 196 is at the logic low level in
order to open the switch 128 (e.g., SW1) as shown by the waveform
296, and the bleeder current 190 is allowed to be generated as
shown by the waveform 290. As shown by the waveform 290, the
bleeder current 190 increases but then becomes smaller with the
decreasing rectified voltage 198 (e.g., VIN) from time t.sub.2 to
time t.sub.3. From time t.sub.3 to time t4, similar to from time to
to time ti, the rectified voltage 198 (e.g., VIN) is at the voltage
level that is close or equal to zero volts as shown by the waveform
298, the LED current 194 (e.g., I.sub.LED) is equal to zero in
magnitude as shown by the waveform 294, the control signal 196 is
at the logic low level in order to open the switch 128 (e.g., SW1)
as shown by the waveform 296, and the bleeder current 190 is
allowed to be generated as shown by the waveform 290. As an
example, from time t.sub.3 to time t4, the bleeder current 190
remains at zero and then increases in magnitude as shown by the
waveform 290.
[0012] As shown in FIG. 2, when the bleeder current 190 drops to
zero in magnitude, the rectified voltage 198 (e.g., VIN) oscillates
as shown by the waveform 298 and the LED current 194 also
oscillates as shown by the waveform 294. Consequently, the LED
current 194 (e.g., I.sub.LED) is not stabile, causing the one or
more LEDs 140 to blink.
[0013] Hence it is highly desirable to improve the techniques
related to LED lighting systems.
3. BRIEF SUMMARY OF THE INVENTION
[0014] Certain embodiments of the present invention are directed to
circuits. More particularly, some embodiments of the invention
provide systems and methods for bleeder control related to Triode
for Alternating Current (TRIAC) dimmers. Merely by way of example,
some embodiments of the invention have been applied to light
emitting diodes (LEDs). But it would be recognized that the
invention has a much broader range of applicability.
[0015] According to some embodiments, a system for controlling one
or more light emitting diodes includes: a current regulator
including a first regulator terminal and a second regulator
terminal, the first regulator terminal being configured to receive
a diode current flowing through the one or more light emitting
diodes, the current regulator being configured to generate a
sensing signal representing the diode current, the second regulator
terminal being configured to output the sensing signal; a bleeder
controller including a first controller terminal and a second
controller terminal, the first controller terminal being configured
to receive the sensing signal from the second regulator terminal,
the bleeder controller being configured to generate a first bleeder
control signal based at least in part on the sensing signal, the
second controller terminal being configured to output the first
bleeder control signal, the first bleeder control signal indicating
whether a bleeder current is allowed or not allowed to be
generated; and a bleeder including a first bleeder terminal and a
second bleeder terminal, the first bleeder terminal being
configured to receive the first bleeder control signal from the
second controller terminal, the second bleeder terminal being
configured to receive a rectified voltage associated with a TRIAC
dimmer and generated by a rectifying bridge; wherein: the bleeder
includes a current controller and a current generator; the current
controller is configured to receive the first bleeder control
signal and generate an input voltage based at least in part on the
first bleeder control signal; and the current generator is
configured to receive the rectified voltage and the input voltage
and generate the bleeder current based at least in part on the
input voltage; wherein, if the first bleeder control signal
indicates that the bleeder current is not allowed to be generated:
the current controller is configured to gradually reduce the input
voltage from a first voltage magnitude at a first time to a second
voltage magnitude at a second time; and the current generator is
configured to gradually reduce the bleeder current from a first
current magnitude at the first time to a second current magnitude
at the second time; wherein the second time follows the first time
by a predetermined duration of time.
[0016] According to certain embodiments, a system for controlling
one or more light emitting diodes includes: a current regulator
including a first regulator terminal and a second regulator
terminal, the first regulator terminal being configured to receive
a diode current flowing through the one or more light emitting
diodes, the current regulator being configured to generate a
sensing signal representing the diode current, the second regulator
terminal being configured to output the sensing signal; a voltage
divider including a first divider terminal and a second divider
terminal, the first divider terminal being configured to receive a
rectified voltage associated with a TRIAC dimmer and generated by a
rectifying bridge, the voltage divider being configured to generate
a converted voltage proportional to the rectified voltage, the
second divider terminal being configured to output the converted
voltage; a bleeder controller including a first controller
terminal, a second controller terminal and a third controller
terminal, the first controller terminal being configured to receive
the converted voltage from the second divider terminal, the second
controller terminal being configured to receive the sensing signal
from the second regulator terminal, the bleeder controller being
configured to generate a first bleeder control signal based at
least in part on the converted voltage, the third controller
terminal being configured to output the first bleeder control
signal, the first bleeder control signal indicating whether a
bleeder current is allowed or not allowed to be generated; and a
bleeder including a first bleeder terminal and a second bleeder
terminal, the first bleeder terminal being configured to receive
the first bleeder control signal from the third controller
terminal, the second bleeder terminal being configured to receive
the rectified voltage; wherein: the bleeder includes a current
controller and a current generator; the current controller is
configured to receive the first bleeder control signal and generate
an input voltage based at least in part on the first bleeder
control signal; and the current generator is configured to receive
the rectified voltage and the input voltage and generate the
bleeder current based at least in part on the input voltage;
wherein, if the first bleeder control signal indicates that the
bleeder current is not allowed to be generated: the current
controller is configured to gradually reduce the input voltage from
a first voltage magnitude at a first time to a second voltage
magnitude at a second time; and the current generator is configured
to gradually reduce the bleeder current from a first current
magnitude at the first time to a second current magnitude at the
second time; wherein the second time follows the first time by a
predetermined duration of time.
[0017] According to some embodiments, a system for controlling one
or more light emitting diodes includes: a current regulator
including a first regulator terminal and a second regulator
terminal, the first regulator terminal being configured to receive
a diode current flowing through the one or more light emitting
diodes, the current regulator being configured to generate a
sensing signal representing the diode current, the second regulator
terminal being configured to output the sensing signal; a voltage
divider including a first divider terminal and a second divider
terminal, the first divider terminal being configured to receive a
rectified voltage associated with a TRIAC dimmer and generated by a
rectifying bridge, the voltage divider being configured to generate
a converted voltage proportional to the rectified voltage, the
second divider terminal being configured to output the converted
voltage; a bleeder controller including a first controller
terminal, a second controller terminal and a third controller
terminal, the first controller terminal being configured to receive
the converted voltage from the second divider terminal, the second
controller terminal being configured to receive the sensing signal
from the second regulator terminal, the bleeder controller being
configured to generate a first bleeder control signal based at
least in part on the converted voltage, the third controller
terminal being configured to output the first bleeder control
signal, the first bleeder control signal indicating whether a
bleeder current is allowed or not allowed to be generated; and a
bleeder including a first bleeder terminal and a second bleeder
terminal, the first bleeder terminal being configured to receive
the first bleeder control signal from the third controller
terminal, the second bleeder terminal being configured to receive
the rectified voltage, the bleeder being configured to generate the
bleeder current based at least in part on the first bleeder control
signal; wherein the bleeder controller is configured to: determine
a phase range within which the TRIAC dimmer is in a conduction
state based on at least information associated with the converted
voltage; and generate a detection signal by comparing a
predetermined conduction phase threshold and the phase range within
which the TRIAC dimmer is in the conduction state; wherein the
bleeder controller is further configured to: if the detection
signal indicates that the phase range within which the TRIAC dimmer
is in the conduction state is larger than the predetermined
conduction phase threshold, generate the first bleeder control
signal based at least in part on the sensing signal; and if the
detection signal indicates that the phase range within which the
TRIAC dimmer is in the conduction state is determined to be smaller
than the predetermined conduction phase threshold, generate the
first bleeder control signal based at least in part on the
converted voltage; wherein: if the first bleeder control signal
indicates that the bleeder current is not allowed to be generated,
the current generator is configured to gradually reduce the bleeder
current from a first current magnitude at a first time to a second
current magnitude at a second time; wherein the second time follows
the first time by a predetermined duration of time.
[0018] According to certain embodiments, a method for controlling
one or more light emitting diodes includes: receiving a diode
current flowing through the one or more light emitting diodes;
generating a sensing signal representing the diode current;
outputting the sensing signal; receiving the sensing signal;
generating a first bleeder control signal based at least in part on
the sensing signal, the first bleeder control signal indicating
whether a bleeder current is allowed or not allowed to be
generated; outputting the first bleeder control signal; receiving
the first bleeder control signal; generating an input voltage based
at least in part on the first bleeder control signal; receiving the
input voltage and a rectified voltage associated with a TRIAC
dimmer: generating the bleeder current based at least in part on
the input voltage; wherein: the generating an input voltage based
at least in part on the first bleeder control signal includes, if
the first bleeder control signal indicates that the bleeder current
is not allowed to be generated, gradually reducing the input
voltage from a first voltage magnitude at a first time to a second
voltage magnitude at a second time; and the generating the bleeder
current based at least in part on the input voltage includes, if
the first bleeder control signal indicates that the bleeder current
is not allowed to be generated, gradually reducing the bleeder
current from a first current magnitude at the first time to a
second current magnitude at the second time; wherein the second
time follows the first time by a predetermined duration of
time.
[0019] According to some embodiments, a method for controlling one
or more light emitting diodes includes: receiving a diode current
flowing through the one or more light emitting diodes; generating a
sensing signal representing the diode current; outputting the
sensing signal; receiving a rectified voltage associated with a
TRIAC dimmer; generating a converted voltage proportional to the
rectified voltage; outputting the converted voltage; receiving the
converted voltage and the sensing signal; generating a first
bleeder control signal based at least in part on the converted
voltage, the first bleeder control signal indicating whether a
bleeder current is allowed or not allowed to be generated;
outputting the first bleeder control signal; receiving the first
bleeder control signal; generating an input voltage based at least
in part on the first bleeder control signal; receiving the input
voltage and the rectified voltage; and generating the bleeder
current based at least in part on the input voltage; wherein: the
generating an input voltage based at least in part on the first
bleeder control signal includes, if the first bleeder control
signal indicates that the bleeder current is not allowed to be
generated, gradually reducing the input voltage from a first
voltage magnitude at a first time to a second voltage magnitude at
a second time; and the generating the bleeder current based at
least in part on the input voltage includes, if the first bleeder
control signal indicates that the bleeder current is not allowed to
be generated, gradually reducing the bleeder current from a first
current magnitude at the first time to a second current magnitude
at the second time; wherein the second time follows the first time
by a predetermined duration of time.
[0020] According to certain embodiments, a method for controlling
one or more light emitting diodes, the method comprising: receiving
a diode current flowing through the one or more light emitting
diodes; generating a sensing signal representing the diode current;
outputting the sensing signal; receiving a rectified voltage
associated with a TRIAC dimmer; generating a converted voltage
proportional to the rectified voltage; outputting the converted
voltage; receive the converted voltage and the sensing signal;
generating a first bleeder control signal based at least in part on
the converted voltage, the first bleeder control signal indicating
whether a bleeder current is allowed or not allowed to be
generated; outputting the first bleeder control signal; receiving
the first bleeder control signal and the rectified voltage; and
generating the bleeder current based at least in part on the input
voltage; wherein the generating a first bleeder control signal
based at least in part on the converted voltage includes:
determining a phase range within which the TRIAC dimmer is in a
conduction state based on at least information associated with the
converted voltage; generating a detection signal by comparing a
predetermined conduction phase threshold and the phase range within
which the TRIAC dimmer is in the conduction state; if the detection
signal indicates that the phase range within which the TRIAC dimmer
is in the conduction state is larger than the predetermined
conduction phase threshold, generating the first bleeder control
signal based at least in part on the sensing signal; and if the
detection signal indicates that the phase range within which the
TRIAC dimmer is in the conduction state is smaller than the
predetermined conduction phase threshold, generating the first
bleeder control signal based at least in part on the converted
voltage; wherein the generating the bleeder current based at least
in part on the input voltage includes, if the first bleeder control
signal indicates that the bleeder current is not allowed to be
generated, gradually reducing the bleeder current from a first
current magnitude at a first time to a second current magnitude at
a second time; wherein the second time follows the first time by a
predetermined duration of time.
[0021] Depending upon embodiment, one or more benefits may be
achieved. These benefits and various additional objects, features
and advantages of the present invention can be fully appreciated
with reference to the detailed description and accompanying
drawings that follow.
4. BRIEF DESCRIPTION OF THE DRAWINGS
[0022] FIG. 1 is a simplified diagram showing a conventional LED
lighting system using a TRIAC dimmer.
[0023] FIG. 2 shows simplified timing diagrams for the conventional
LED lighting system using the TRIAC dimmer as shown in FIG. 1.
[0024] FIG. 3 is a simplified circuit diagram showing an LED
lighting system according to some embodiments of the present
invention.
[0025] FIG. 4 is a simplified circuit diagram showing the bleeder
control unit of the LED lighting system as shown in FIG. 3
according to certain embodiments of the present invention.
[0026] FIG. 5 shows simplified timing diagrams for the LED lighting
system as shown in FIG. 3 according to certain embodiments of the
present invention.
[0027] FIG. 6 is a simplified circuit diagram showing an LED
lighting system according to certain embodiments of the present
invention.
[0028] FIG. 7 is a simplified circuit diagram showing the bleeder
control unit of the LED lighting system as shown in FIG. 6
according to some embodiments of the present invention.
[0029] FIG. 8 shows simplified timing diagrams for the LED lighting
system as shown in FIG. 6 according to certain embodiments of the
present invention.
[0030] FIG. 9 is a simplified circuit diagram showing an LED
lighting system according to some embodiments of the present
invention.
[0031] FIG. 10 is a simplified circuit diagram showing the bleeder
control unit of the LED lighting system as shown in FIG. 9
according to certain embodiments of the present invention.
[0032] FIG. 11 shows simplified timing diagrams for the LED
lighting system as shown in FIG. 9 if the phase range within which
the TRIAC dimmer is in the conduction state (e.g., on state) is
smaller than the predetermined conduction phase threshold according
to certain embodiments of the present invention.
[0033] FIG. 12 is a simplified circuit diagram showing an LED
lighting system according to certain embodiments of the present
invention.
[0034] FIG. 13 is a simplified circuit diagram showing the bleeder
control unit of the LED lighting system as shown in FIG. 12
according to certain embodiments of the present invention.
[0035] FIG. 14 is a simplified diagram showing a method for the LED
lighting system as shown in FIG. 9 according to some embodiments of
the present invention.
[0036] FIG. 15 is a simplified diagram showing a method for the LED
lighting system as shown in FIG. 12 according to certain
embodiments of the present invention.
5. DETAILED DESCRIPTION OF THE INVENTION
[0037] Certain embodiments of the present invention are directed to
circuits. More particularly, some embodiments of the invention
provide systems and methods for bleeder control related to Triode
for Alternating Current (TRIAC) dimmers. Merely by way of example,
some embodiments of the invention have been applied to light
emitting diodes (LEDs). But it would be recognized that the
invention has a much broader range of applicability.
[0038] Referring to FIG. 1 and FIG. 2, the input circuit for the
rectified voltage 198 (e.g., VIN) includes one or more parasitic
capacitors for generating the bleeder current 190 (e.g.,
I.sub.bleed) according to some embodiments. For example, when the
bleeder current 190 drops to zero in magnitude, the current of the
input circuit oscillates, causing the rectified voltage 198 (e.g.,
VIN) to also oscillate as shown by the waveform 298. As an example,
the oscillation in the rectified voltage 198 (e.g., VIN) leads to
oscillation in the LED current 194 as shown by the waveform 294,
causing instability in the conduction state (e.g., on state) and
also change in the conduction phase angle of the TRIAC dimmer 150.
Consequently, the LED current 194 (e.g., I.sub.LED) is not stabile,
causing the one or more LEDs 140 to blink, according to certain
embodiments.
[0039] FIG. 3 is a simplified circuit diagram showing an LED
lighting system according to some embodiments of the present
invention. This diagram is merely an example, which should not
unduly limit the scope of the claims. One of ordinary skill in the
art would recognize many variations, alternatives, and
modifications. As shown in FIG. 3, the LED lighting system 300
includes a TRIAC dimmer 350, a rectifying bridge 352 (e.g., a full
wave rectifying bridge), a fuse 354, one or more LEDs 340, and a
control system. As an example, the control system of the LED
lighting system 300 includes a constant current unit 310 (e.g., a
current regulator), a bleeder unit 320, and a bleeder control unit
330. Although the above has been shown using a selected group of
components for the LED lighting system, there can be many
alternatives, modifications, and variations. For example, some of
the components may be expanded and/or combined. Other components
may be inserted to those noted above. Depending upon the
embodiment, the arrangement of components may be interchanged with
others replaced. Further details of these components are found
throughout the present specification.
[0040] As shown in FIG. 3, the rectifying bridge 352 (e.g., a full
wave rectifying bridge) is coupled to the TRIAC dimmer 350 through
the fuse 354, and an AC input voltage 366 (e.g., VAC) is received
by the TRIAC dimmer 350 and is also rectified by the rectifying
bridge 352 to generate a rectified voltage 398 (e.g., VIN)
according to certain embodiments. As an example, the rectified
voltage 398 does not fall below the ground voltage (e.g., zero
volts).
[0041] According to some embodiments, the constant current unit 310
includes two terminals, one of which is coupled to the one or more
LEDs 340 and the other of which is coupled to the bleeder control
unit 330. As an example, the bleeder control unit 330 includes two
terminals, one of which is coupled to the constant current unit 310
and the other of which is coupled to the bleeder unit 320. For
example, the bleeder unit 320 includes two terminals, one of which
is coupled to the bleeder control unit 330 and the other of which
is configured to receive the rectified voltage 398 (e.g., VIN).
[0042] According to certain embodiments, the bleeder control unit
330 is configured to detect a change of an LED current 394 (e.g.,
I.sub.LED) that flows through the one or more LEDs 340, and based
at least in part on the change of the LED current 394, to allow or
not allow the bleeder unit 320 to generate a bleeder current 390.
For example, the bleeder control unit 330 receives from the
constant current unit 310 a sensing voltage 382 (e.g., V.sub.sense)
that represents the LED current 394 (e.g., I.sub.LED), and the
bleeder control unit 330 generates, based at least in part on the
sensing voltage 382, a control signal 384 to allow or not allow the
bleeder unit 320 to generate the bleeder current 390.
[0043] In some embodiments, the constant current unit 310 includes
a transistor 360, a resistor 362, and an amplifier 364. For
example, the amplifier 364 includes two input terminal and an
output terminal. As an example, one of the two input terminals
receives a reference voltage 370 (e.g., V.sub.ref0), and the other
of the two input terminals is coupled to the resistor 362 and
configured to generate the sensing voltage 382 (e.g., V.sub.sense).
For example, the sensing voltage 382 (e.g., V.sub.sense) is equal
to the LED current 394 (e.g., I.sub.LED) multiplied by the
resistance (e.g., R.sub.1) of the resistor 362.
[0044] In certain embodiments, if the sensing voltage 382 (e.g.,
V.sub.sense) indicates that the LED current 394 is higher than a
threshold current (e.g., a holding current of the TRIAC dimmer
350), the bleeder control unit 330 outputs the control signal 384
to the bleeder unit 320, and the control signal 384 does not allow
the bleeder unit 320 to generate the bleeder current 390. In some
embodiments, if the sensing voltage 382 indicates that the LED
current 394 is lower than the threshold current (e.g., a holding
current of the TRIAC dimmer 350), the bleeder control unit 330
outputs the control signal 384 to the bleeder unit 320, and the
control signal 384 allows the bleeder unit 320 to generate the
bleeder current 390. As an example, the bleeder unit 320 receives
the control signal 384 from the bleeder control unit 330, and if
the control signal 384 allows the bleeder unit 320 to generate the
bleeder current 390, the bleeder unit 320 generates the bleeder
current 390 so that the TRIAC dimmer 350 can operate properly.
[0045] As shown in FIG. 3, the bleeder unit 320 includes a
bleeder-current generation sub-unit 3210 and a bleeder-current
control sub-unit 3220 according to certain embodiments. In some
embodiments, the bleeder-current generation sub-unit 3210 includes
an amplifier 322, a transistor 324, and a resistor 326. In certain
embodiments, the bleeder-current control sub-unit 3220 includes an
amplifier 332, a switch 334, a resistor 336, and a capacitor
338.
[0046] In some examples, if the transistor 324 is in the saturation
region, the bleeder current 390 is determined as follows:
I bleed = V p R 2 ( Equation 2 ) ##EQU00002##
[0047] where I.sub.bleed represents the bleeder current 390,
V.sub.p represents a voltage 386 received by the amplifier 322, and
R.sub.2 represents the resistance value of the resistor 326. In
certain examples, the amplifier 322 includes a positive input
terminal (e.g., the "+" terminal) and a negative input terminal
(e.g., the "-" terminal). For example, the voltage 386 is received
by the positive input terminal of the amplifier 322. As an example,
the voltage 386 is controlled by the switch 334, which makes the
voltage 386 equal to either the ground voltage (e.g., zero volts)
or a reference voltage 388 (e.g., V.sub.ref1). For example, the
reference voltage 388 is received by the amplifier 332 and is
larger than zero volts.
[0048] According to some embodiments, if the sensing voltage 382
indicates that the LED current 394 is lower than the threshold
current, the control signal 384 received by the bleeder unit 320
sets the switch 334 so that the positive input terminal (e.g., the
"+" terminal) of the amplifier 322 is biased to the reference
voltage 388 through the amplifier 332. For example, if the sensing
voltage 382 indicates that the LED current 394 is lower than the
threshold current, the voltage 386 is equal to the reference
voltage 388 and the bleeder current 390 is generated (e.g., the
bleeder current 390 being larger than zero in magnitude).
[0049] According to certain embodiments, if the sensing voltage 382
indicates that the LED current 394 is higher than the threshold
current, the control signal 384 received by the bleeder unit 320
sets the switch 334 so that the positive input terminal (e.g., the
"+" terminal) of the amplifier 322 is biased to the ground voltage
through the resistor 336. For example, if the sensing voltage 382
indicates that the LED current 394 is higher than the threshold
current, the voltage 386 is equal to the ground voltage (e.g., zero
volts) and the bleeder current 390 is not generated (e.g., the
bleeder current 390 being equal to zero).
[0050] In certain embodiments, if the LED current 394 changes from
being lower than the threshold current to being higher than the
threshold current, the control signal 384, through the switch 334,
changes the voltage 386 from being equal to the reference voltage
388 (e.g., larger than zero volts) to being equal to the ground
voltage (e.g., equal to zero volts) so that the bleeder current 390
changes from being larger than zero to being equal to zero. As
shown in FIG. 3, the resistor 336 and the capacitor 338 are parts
of an RC filtering circuit, which slows down the decrease of the
voltage 386 from the reference voltage 388 (e.g., larger than zero
volts) to the ground voltage (e.g., equal to zero volts) and also
slows down the decrease of the bleeder current 390 from being
larger than zero to being equal to zero according to some
embodiments. For example, the bleeder unit 320 is configured to
turning off the bleeder current 390 gradually (e.g., slowly) during
a predetermined time duration, and the length of the predetermined
time duration depends on the resistance of the resistor 336 and the
capacitance of the capacitor 338.
[0051] In certain embodiments, if the LED current 394 changes from
being higher than the threshold current to being lower than the
threshold current, the control signal 384, through the switch 334,
changes the voltage 386 from being equal to the ground voltage
(e.g., equal to zero volts) to being equal to the reference voltage
388 (e.g., larger than zero volts) so that the bleeder current 390
changes from being equal to zero to being larger than zero in order
to for the TRIAC dimmer 350 to operate properly. In some examples,
when the voltage 386 is biased to the reference voltage 388 (e.g.,
larger than zero volts), if the transistor 324 is in the saturation
region, the bleeder current 390 is determined as follows:
I bleed = V ref 1 R 2 ( Equation 3 ) ##EQU00003##
[0052] where I.sub.bleed represents the bleeder current 390,
V.sub.ref1 represents the reference voltage 388, and R.sub.2
represents the resistance value of the resistor 326.
[0053] FIG. 4 is a simplified circuit diagram showing the bleeder
control unit 330 of the LED lighting system 300 as shown in FIG. 3
according to certain embodiments of the present invention. This
diagram is merely an example, which should not unduly limit the
scope of the claims. One of ordinary skill in the art would
recognize many variations, alternatives, and modifications. As
shown in FIG. 4, the bleeder control unit 330 includes a comparator
3310 and a delay sub-unit 3320. Although the above has been shown
using a selected group of components for the bleeder control unit,
there can be many alternatives, modifications, and variations. For
example, some of the components may be expanded and/or combined.
Other components may be inserted to those noted above. Depending
upon the embodiment, the arrangement of components may be
interchanged with others replaced. Further details of these
components are found throughout the present specification.
[0054] In some embodiments, the comparator 3310 includes input
terminals 402 and 404 and an output terminal 406. As an example,
the input terminal 402 receives the sensing voltage 382 (e.g.,
V.sub.sense), and the input terminal 404 receives a threshold
voltage 490 (e.g., V.sub.th). For example, the threshold voltage
490 (e.g., V.sub.th) is smaller than the reference voltage 370
(e.g., V.sub.ref0) for the constant current unit 310. As an
example, the threshold voltage 490 (e.g., V.sub.th) is equal to the
threshold current (e.g., the holding current of the TRIAC dimmer
350) multiplied by the resistance (e.g., R.sub.1) of the resistor
362. In certain examples, if the sensing voltage 382 (e.g.,
V.sub.sense) is larger than the threshold voltage 490 (e.g.,
V.sub.th), the LED current 394 is larger than the threshold current
(e.g., the holding current of the TRIAC dimmer 350). In some
examples, if the sensing voltage 382 (e.g., V.sub.sense) is smaller
than the threshold voltage 490 (e.g., V.sub.th), the LED current
394 is smaller than the threshold current (e.g., the holding
current of the TRIAC dimmer 350).
[0055] In certain embodiments, the comparator 3310 compares the
sensing voltage 382 (e.g., V.sub.sense) and the threshold voltage
490 (e.g., V.sub.th) and generates a comparison signal 492. For
example, if the sensing voltage 382 (e.g., V.sub.sense) is larger
than the threshold voltage 490 (e.g., V.sub.th), the comparator
3310 generates the comparison signal 492 at a logic high level. As
an example, if the sensing voltage 382 (e.g., V.sub.sense) is
smaller than the threshold voltage 490 (e.g., V.sub.th), the
comparator 3310 generates the comparison signal 492 at a logic low
level. In some embodiments, if the sensing voltage 382 (e.g.,
V.sub.sense) changes from being smaller than the threshold voltage
490 (e.g., V.sub.th) to being larger than the threshold voltage 490
(e.g., V.sub.th), the comparison signal 492 changes from the logic
low level to the logic high level. As an example, the comparator
3310 outputs the comparison signal 492 at the output terminal
406.
[0056] According to certain embodiments, the comparison signal 492
is received by the delay sub-unit 3320, which in response generates
the control signal 384. For example, if the comparison signal 492
changes from the logic low level to the logic high level, the delay
sub-unit 3320, after a predetermined delay (e.g., after t.sub.d),
changes the control signal 384 from the logic low level to the
logic high level. As an example, if the comparison signal 492
changes from the logic high level to the logic low level, the delay
sub-unit 3320, without any predetermined delay (e.g., without
t.sub.d), changes the control signal 384 from the logic high level
to the logic low level.
[0057] As shown in FIG. 3, if the control signal 384 is at the
logic high level, the switch 334 is set to bias the voltage 386 to
the ground voltage (e.g., being equal to zero volts), and if the
control signal 384 is at the logic low level, the switch 334 is set
to bias the voltage 386 to the reference voltage 388 (e.g., being
larger than zero volts), according to some embodiments. For
example, if the control signal 384 changes from the logic high
level to the logic low level, the voltage 386 changes from the
ground voltage (e.g., being equal to zero volts) to the reference
voltage 388 (e.g., being larger than zero volts). As an example, if
the control signal 384 changes from the logic low level to the
logic high level, the voltage 386 changes from the reference
voltage 388 (e.g., being larger than zero volts) to the ground
voltage (e.g., being equal to zero volts).
[0058] In certain embodiments, if the LED current 394 changes from
being lower than the threshold current to being higher than the
threshold current, the bleeder current 390, after the predetermined
delay (e.g., after t.sub.d), changes gradually (e.g., slowly) from
being larger than zero to being equal to zero during the
predetermined time duration. For example, the predetermined delay
(e.g., t.sub.d) is provided by the delay sub-unit 3320. As an
example, the length of the predetermined time duration depends on
the resistance of the resistor 336 and the capacitance of the
capacitor 338. In some embodiments, if the LED current 394 changes
from being higher than the threshold current to being lower than
the threshold current, the bleeder current 390, without any
predetermined delay (e.g., without t.sub.d), changes from being
equal to zero to being larger than zero.
[0059] FIG. 5 shows simplified timing diagrams for the LED lighting
system 300 as shown in FIG. 3 according to certain embodiments of
the present invention. These diagrams are merely examples, which
should not unduly limit the scope of the claims. One of ordinary
skill in the art would recognize many variations, alternatives, and
modifications. The waveform 598 represents the rectified voltage
398 (e.g., VIN) as a function of time, the waveform 594 represents
the LED current 394 (e.g., I.sub.LED) as a function of time, the
waveform 586 represents the voltage 386 (e.g., V.sub.p) as a
function of time, and the waveform 590 represents the bleeder
current 390 (e.g., bleed) as a function of time.
[0060] In some embodiments, when the LED lighting system 300 works
properly, the TRIAC dimmer 350 clips parts of a waveform for the AC
input voltage 366 (e.g., VAC). As an example, from time to to time
ti, the rectified voltage 398 (e.g., VIN) is at a voltage level
that is close or equal to zero volts as shown by the waveform 598,
the LED current 394 (e.g., I.sub.LED) is equal to zero in magnitude
as shown by the waveform 594, the voltage 386 (e.g., V.sub.p) is
equal to the reference voltage 388 and larger than zero in
magnitude as shown by the waveform 586, and the bleeder current 390
is allowed to be generated as shown by the waveform 590. As an
example, from time to to time ti, the bleeder current 390 is
allowed to be generated as shown by the waveform 590, so the
bleeder current 390 remains at zero and then increases in magnitude
as shown by the waveform 590.
[0061] As shown in FIG. 5, from time t.sub.1 to time t.sub.4, the
rectified voltage 398 (e.g., VIN) is at a high voltage level (e.g.,
a high voltage level that is not constant) as shown by the waveform
598, and the LED current 394 (e.g., I.sub.LED) is at a high current
level as shown by the waveform 594 according to some embodiments.
In certain examples, from time t.sub.1 to time t.sub.2, the voltage
386 (e.g., V.sub.p) remains equal to the reference voltage 388 and
larger than zero in magnitude as shown by the waveform 586, and the
bleeder current 390 is at a high current level (e.g., being larger
than zero) as shown by the waveform 590. In some examples, the time
duration from time t.sub.1 to time t.sub.2 is the predetermined
delay (e.g., t.sub.d) provided by the delay sub-unit 3320.
[0062] In some examples, from time t.sub.2 to time t3, the voltage
386 (e.g., V.sub.p) changes from being equal to the reference
voltage 388 (e.g., larger than zero volts) to being equal to the
ground voltage (e.g., equal to zero volts) gradually (e.g., slowly)
during the predetermined time duration as shown by the waveform
586, and the bleeder current 390 also changes from being equal to
the high current level (e.g., being larger than zero) to being
equal to zero gradually (e.g., slowly) during the predetermined
time duration as shown by the waveform 590. As an example, the time
duration from time t.sub.2 to time t.sub.3 is equal to the
predetermined time duration, and the length of the predetermined
time duration depends on the resistance of the resistor 336 and the
capacitance of the capacitor 338. In some examples, from time
t.sub.3 to time t.sub.4, the voltage 386 (e.g., V.sub.p) remains
equal to the ground voltage (e.g., equal to zero volts) as shown by
the waveform 586, and the bleeder current 390 also remains equal to
zero as shown by the waveform 590.
[0063] As shown in FIG. 5, from time t.sub.2 to time t.sub.4, the
bleeder current 390 is not allowed to be generated as shown by the
waveform 590, so the bleeder current 390 changes from being equal
to the high current level (e.g., being larger than zero) to being
equal to zero gradually (e.g., slowly) from time t.sub.2 to time
t.sub.3 (e.g., during the predetermined time duration) and then the
bleeder current 390 remains equal to zero from time t.sub.3 to time
t.sub.4 according to certain embodiments.
[0064] From time t.sub.4 to time t.sub.5, the rectified voltage 398
(e.g., VIN) changes from the high voltage level to a low voltage
level (e.g., a low voltage level that is not constant but larger
than zero volts) as shown by the waveform 598, the LED current 394
(e.g., I.sub.LED) is equal to zero in magnitude as shown by the
waveform 594, the voltage 386 (e.g., V.sub.p) is equal to the
reference voltage 388 (e.g., larger than zero volts) as shown by
the waveform 586, and the bleeder current 390 is allowed to be
generated as shown by the waveform 590, according to some
embodiments. For example, as shown by the waveform 590, the bleeder
current 390 increases but then becomes smaller with the decreasing
rectified voltage 398 (e.g., VIN) from time t.sub.4 to time
t.sub.5. From time is t.sub.0 time t.sub.6, similar to from time to
to time ti, the rectified voltage 398 (e.g., VIN) is at the voltage
level that is close or equal to zero volts as shown by the waveform
598, the LED current 394 (e.g., I.sub.LED) is equal to zero in
magnitude as shown by the waveform 594, the voltage 386 (e.g.,
V.sub.p) is equal to the reference voltage 388 and larger than zero
in magnitude as shown by the waveform 586, and the bleeder current
390 is allowed to be generated as shown by the waveform 590. As an
example, from time is to time t6, the bleeder current 390 remains
at zero and then increases in magnitude as shown by the waveform
590.
[0065] As shown in FIG. 3 and FIG. 4, the LED lighting system 300
provides the RC filtering circuit that includes the resistor 336
and the capacitor 338 in order to control how fast the bleeder
current 390 changes from being equal to the high current level
(e.g., being larger than zero) to being equal to zero according to
certain embodiments. In some examples, the bleeder current 390
changes from being equal to the high current level (e.g., being
larger than zero) to being equal to zero gradually (e.g., slowly)
during the predetermined time duration, and the length of the
predetermined time duration depends on the resistance of the
resistor 336 and the capacitance of the capacitor 338. In certain
examples, the LED lighting system 300 uses the delay sub-unit 3320
as part of the bleeder control unit 330 in order to cause the
predetermined delay (e.g., t.sub.d) after the LED current 394
becomes higher than the threshold current (e.g., a holding current
of the TRIAC dimmer 350) but before the voltage 386 starts
decreasing from the reference voltage 388 and the bleeder current
390 also starts decreasing from the high current level (e.g., being
larger than zero).
[0066] In some embodiments, the predetermined delay (e.g., t.sub.d)
helps to stabilize the conduction state (e.g., on state) of the
TRIAC dimmer 350. In certain embodiments, the gradual (e.g., slow)
reduction of the bleeder current 390 during the predetermined time
duration helps to reduce (e.g., eliminate) the oscillation of the
rectified voltage 398 (e.g., VIN) and also helps to stabilize the
LED current 394 (e.g., I.sub.LED) to reduce (e.g., eliminate)
blinking of the one or more LEDs 340.
[0067] As discussed above and further emphasized here, FIG. 3, FIG.
4 and FIG. 5 are merely examples, which should not unduly limit the
scope of the claims. One of ordinary skill in the art would
recognize many variations, alternatives, and modifications. As an
example, two or more levels of control mechanisms are used by the
bleeder-current control sub-unit so that gradual (e.g., slow)
reduction of the bleeder current 390 is accomplished in two or more
stages respectively to further reduce (e.g., eliminate) the
oscillation of the rectified voltage 398 (e.g., VIN) and further
reduce (e.g., eliminate) blinking of the one or more LEDs 340.
[0068] FIG. 6 is a simplified circuit diagram showing an LED
lighting system according to certain embodiments of the present
invention. This diagram is merely an example, which should not
unduly limit the scope of the claims. One of ordinary skill in the
art would recognize many variations, alternatives, and
modifications. As shown in FIG. 6, the LED lighting system 600
includes a TRIAC dimmer 650, a rectifying bridge 652 (e.g., a full
wave rectifying bridge), a fuse 654, one or more LEDs 640, and a
control system. As an example, the control system of the LED
lighting system 600 includes a constant current unit 610 (e.g., a
current regulator), a bleeder unit 620, and a bleeder control unit
630. Although the above has been shown using a selected group of
components for the LED lighting system, there can be many
alternatives, modifications, and variations. For example, some of
the components may be expanded and/or combined. Other components
may be inserted to those noted above. Depending upon the
embodiment, the arrangement of components may be interchanged with
others replaced. Further details of these components are found
throughout the present specification.
[0069] As shown in FIG. 6, the rectifying bridge 652 (e.g., a full
wave rectifying bridge) is coupled to the TRIAC dimmer 650 through
the fuse 654, and an AC input voltage 666 (e.g., VAC) is received
by the TRIAC dimmer 650 and is also rectified by the rectifying
bridge 652 to generate a rectified voltage 698 (e.g., VIN)
according to certain embodiments. As an example, the rectified
voltage 698 does not fall below the ground voltage (e.g., zero
volts).
[0070] According to some embodiments, the constant current unit 610
includes two terminals, one of which is coupled to the one or more
LEDs 640 and the other of which is coupled to the bleeder control
unit 630. As an example, the bleeder control unit 630 includes two
terminals, one of which is coupled to the constant current unit 610
and the other of which is coupled to the bleeder unit 620. For
example, the bleeder unit 620 includes two terminals, one of which
is coupled to the bleeder control unit 630 and the other of which
is configured to receive the rectified voltage 698 (e.g., VIN).
[0071] According to certain embodiments, the bleeder control unit
630 is configured to detect a change of an LED current 694 (e.g.,
I.sub.LED) that flows through the one or more LEDs 640, and based
at least in part on the change of the LED current 694, to allow or
not allow the bleeder unit 620 to generate a bleeder current 690.
For example, the bleeder control unit 630 receives from the
constant current unit 610 a sensing voltage 682 (e.g., V.sub.sense)
that represents the LED current 694 (e.g., I.sub.LED), and the
bleeder control unit 630 generates, based at least in part on the
sensing voltage 682, control signals 384.sub.1 and 384.sub.2 to
allow or not allow the bleeder unit 620 to generate the bleeder
current 690.
[0072] In some embodiments, the constant current unit 610 includes
a transistor 660, a resistor 662, and an amplifier 664. For
example, the amplifier 664 includes two input terminal and an
output terminal. As an example, one of the two input terminals
receives a reference voltage 670 (e.g., V.sub.ref0), and the other
of the two input terminals is coupled to the resistor 662 and
configured to generate the sensing voltage 682 (e.g., V.sub.sense).
For example, the sensing voltage 682 (e.g., V.sub.sense) is equal
to the LED current 694 (e.g., I.sub.LED) multiplied by the
resistance (e.g., R.sub.1) of the resistor 662.
[0073] In certain embodiments, if the sensing voltage 682 (e.g.,
V.sub.sense) indicates that the LED current 694 is higher than a
threshold current (e.g., a holding current of the TRIAC dimmer
650), the bleeder control unit 630 outputs the control signals
684.sub.1 and 684.sub.2 to the bleeder unit 620, and the control
signals 684.sub.1 and 684.sub.2 do not allow the bleeder unit 620
to generate the bleeder current 690. In some embodiments, if the
sensing voltage 682 indicates that the LED current 694 is lower
than the threshold current (e.g., a holding current of the TRIAC
dimmer 650), the bleeder control unit 630 outputs the control
signals 684.sub.1 and 684.sub.2 to the bleeder unit 620, and the
control signals 684.sub.1 and 684.sub.2 allow the bleeder unit 620
to generate the bleeder current 690. As an example, the bleeder
unit 620 receives the control signals 684.sub.1 and 684.sub.2 from
the bleeder control unit 630, and if the control signals 684.sub.1
and 6842 allow the bleeder unit 620 to generate the bleeder current
690, the bleeder unit 620 generates the bleeder current 690 so that
the TRIAC dimmer 650 can operate properly.
[0074] As shown in FIG. 6, the bleeder unit 620 includes a
bleeder-current generation sub-unit 6210 and a bleeder-current
control sub-unit 622.sub.0 according to certain embodiments. In
some embodiments, the bleeder-current generation sub-unit 6210
includes an amplifier 622, a transistor 624, and a resistor 626. In
certain embodiments, the bleeder-current control sub-unit 622.sub.0
includes amplifiers 632.sub.1 and 6322, switches 6341 and 6342, a
resistor 636, and a capacitor 638.
[0075] In certain examples, if the control signal 684.sub.1 is at a
logic low level, the positive input terminal (e.g., the "+"
terminal) of the amplifier 622 is coupled to the output terminal of
the amplifier 632.sub.1 through the switch 634.sub.1, and if the
control signal 684.sub.1 is at a logic high level, the positive
input terminal (e.g., the "+" terminal) of the amplifier 622 is
coupled to the output terminal of the amplifier 632.sub.2 through
the switch 634.sub.1 and the resistor 636. In some examples, if the
control signal 684.sub.2 is at the logic high level, the positive
input terminal (e.g., the "+" terminal) of the amplifier 632.sub.2
is biased to the reference voltage 688.sub.2 (e.g., V.sub.ref2)
through the switch 634.sub.2, and if the control signal 684.sub.2
is at the logic low level, the positive input terminal (e.g., the
"+" terminal) of the amplifier 632.sub.2 is biased to the ground
voltage (e.g., zero volts) through the switch 634.sub.2.
[0076] In some examples, if the transistor 624 is in the saturation
region, the bleeder current 690 is determined as follows:
I bleed = V p R 2 ( Equation 4 ) ##EQU00004##
[0077] where I.sub.bleed represents the bleeder current 690,
V.sub.p represents a voltage 686 received by the amplifier 622, and
R.sub.2 represents the resistance value of the resistor 626. In
certain examples, the amplifier 622 includes a positive input
terminal (e.g., the "+" terminal) and a negative input terminal
(e.g., the "-" terminal). For example, the voltage 686 is received
by the positive input terminal of the amplifier 622. As an example,
the voltage 686 is controlled by the switch 634.sub.1, which makes
the voltage 686 equal to either the output voltage of the amplifier
632.sub.2 or a reference voltage 688.sub.1 (e.g., V.sub.ref1). For
example, the reference voltage 688.sub.1 is received by the
amplifier 632.sub.1 (e.g., received by the positive terminal of the
amplifier 632.sub.1) and is larger than zero volts.
[0078] According to some embodiments, if the sensing voltage 682
indicates that the LED current 694 is lower than the threshold
current, the control signal 684.sub.1 received by the bleeder unit
620 sets the switch 634.sub.1 so that the positive input terminal
(e.g., the "+" terminal) of the amplifier 622 is biased to the
reference voltage 688.sub.1 through the amplifier 632.sub.1. For
example, if the sensing voltage 682 indicates that the LED current
694 is lower than the threshold current, the voltage 686 is equal
to the reference voltage 688.sub.1 and the bleeder current 690 is
generated (e.g., the bleeder current 690 being larger than zero in
magnitude).
[0079] According to certain embodiments, if the sensing voltage 682
indicates that the LED current 694 is higher than the threshold
current, the control signal 684.sub.1 received by the bleeder unit
620 sets the switch 634.sub.1 so that the positive input terminal
(e.g., the "+" terminal) of the amplifier 622 is biased to the
output voltage of the amplifier 632.sub.2 through the resistor 636.
For example, if the sensing voltage 682 indicates that the LED
current 694 is higher than the threshold current, the voltage 686
is equal to the output voltage of the amplifier 632.sub.2. As an
example, the output voltage of the amplifier 632.sub.2 is lower
than the reference voltage 688.sub.1 but still larger than zero
volts. For example, if the voltage 686 is equal to the output
voltage of the amplifier 632.sub.2, the bleeder current 690 is
generated (e.g., the bleeder current 690 being larger than zero in
magnitude) but is smaller than the bleeder current 690 generated
when the voltage 686 is equal to the reference voltage
688.sub.1.
[0080] In certain embodiments, if the LED current 694 changes from
being lower than the threshold current to being higher than the
threshold current, the control signal 684.sub.1, through the switch
634.sub.1, changes the voltage 686 from being equal to the
reference voltage 688.sub.1 (e.g., larger than zero volts) to being
equal to the output voltage of the amplifier 632.sub.2 (e.g., lower
than the reference voltage 688.sub.1 but still larger than zero
volts) so that the bleeder current 690 changes from being equal to
a larger magnitude to being equal to a smaller magnitude (e.g., a
smaller magnitude that is larger than zero). As shown in FIG. 6,
the resistor 636 and the capacitor 638 are parts of an RC filtering
circuit, which slows down the decrease of the voltage 686 from the
reference voltage 688.sub.1 to the output voltage of the amplifier
632.sub.2 (e.g., lower than the reference voltage 688.sub.1 but
still larger than zero volts) and also slows down the decrease of
the bleeder current 690 from being equal to the larger magnitude to
being equal to the smaller magnitude (e.g., the smaller magnitude
that is larger than zero) according to some embodiments. For
example, the bleeder unit 620 is configured to reduce the bleeder
current 690 gradually (e.g., slowly) during a predetermined time
duration, and the length of the predetermined time duration depends
on the resistance of the resistor 636 and the capacitance of the
capacitor 638.
[0081] In certain embodiments, if the LED current 694 changes from
being higher than the threshold current to being lower than the
threshold current, the control signal 6841, through the switch
6341, changes the voltage 686 from being equal to the output
voltage of the amplifier 632.sub.2 (e.g., lower than the reference
voltage 6881) to being equal to the reference voltage 688.sub.1
(e.g., larger than zero volts) so that the bleeder current 690
changes from being equal to the smaller magnitude to being equal to
the larger magnitude in order to for the TRIAC dimmer 650 to
operate properly. In some examples, when the voltage 686 is biased
to the reference voltage 688.sub.1 (e.g., larger than zero volts),
if the transistor 624 is in the saturation region, the bleeder
current 690 is determined as follows:
I bleed = V ref 1 R 2 ( Equation 5 ) ##EQU00005##
[0082] where I.sub.bleed represents the bleeder current 690,
V.sub.ref1 represents the reference voltage 6881, and R.sub.2
represents the resistance value of the resistor 626.
[0083] According to some embodiments, if the sensing voltage 682
indicates that the LED current 694 is lower than the threshold
current, the control signal 684.sub.2 received by the bleeder unit
620 sets the switch 634.sub.2 so that the output terminal of the
amplifier 632.sub.2 is biased to a reference voltage 688.sub.2
(e.g., V.sub.ref2) through the amplifier 632.sub.2. For example,
the reference voltage 688.sub.2 is received by the amplifier
632.sub.2 (e.g., received by the positive terminal of the amplifier
632.sub.2) and is larger than zero volts. As an example, the
reference voltage 688.sub.2 is smaller than the reference voltage
688.sub.1. For example, if the voltage 686 is set to being equal to
the output voltage of the amplifier 632.sub.2 and the output
terminal of the amplifier 632.sub.2 is biased to the reference
voltage 688.sub.2 through the amplifier 632.sub.2, the voltage 686
is equal to the reference voltage 688.sub.2.
[0084] In some examples, when the voltage 686 is biased to the
reference voltage 688.sub.2 (e.g., larger than zero volts), if the
transistor 624 is in the saturation region, the bleeder current 690
is determined as follows:
I bleed = V ref 2 R 2 ( Equation 6 ) ##EQU00006##
[0085] where I.sub.bleed represents the bleeder current 690,
V.sub.ref2 represents the reference voltage 688.sub.2, and R.sub.2
represents the resistance value of the resistor 626.
[0086] According to certain embodiments, if the sensing voltage 682
indicates that the LED current 694 is higher than the threshold
current, the control signal 684.sub.2 received by the bleeder unit
620 sets the switch 6342 so that the output terminal of the
amplifier 632.sub.2 is biased to the ground voltage (e.g., zero
volts). For example, if the sensing voltage 682 indicates that the
LED current 694 is higher than the threshold current, the output
voltage of the amplifier 632.sub.2 is equal to the ground voltage
(e.g., zero volts). As an example, if the voltage 686 is set to
being equal to the output voltage of the amplifier 632.sub.2 and
the output terminal of the amplifier 632.sub.2 is biased to the
ground voltage (e.g., zero volts), the voltage 686 is equal to the
ground voltage (e.g., zero volts).
[0087] In certain embodiments, if the LED current 694 changes from
being lower than the threshold current to being higher than the
threshold current, the control signal 684.sub.2, through the switch
634.sub.2, changes the output voltage of the amplifier 632.sub.2
from being equal to the reference voltage 688.sub.2 to being equal
to the ground voltage (e.g., zero volts). As shown in FIG. 6, if
the voltage 686 is set to being equal to the output voltage of the
amplifier 632.sub.2, the resistor 636 and the capacitor 638 are
parts of the RC filtering circuit, which slows down the decrease of
the voltage 686 from the reference voltage 688.sub.2 to the ground
voltage (e.g., zero volts) and also slows down the decrease of the
bleeder current 690 to zero according to some embodiments. For
example, the bleeder unit 620 is configured to reduce the bleeder
current 690 gradually (e.g., slowly) during a predetermined time
duration, and the length of the predetermined time duration depends
on the resistance of the resistor 636 and the capacitance of the
capacitor 638.
[0088] FIG. 7 is a simplified circuit diagram showing the bleeder
control unit 630 of the LED lighting system 600 as shown in FIG. 6
according to some embodiments of the present invention. This
diagram is merely an example, which should not unduly limit the
scope of the claims. One of ordinary skill in the art would
recognize many variations, alternatives, and modifications. As
shown in FIG. 7, the bleeder control unit 630 includes a comparator
631.sub.0 and delay sub-units 632.sub.0 and 633.sub.0. Although the
above has been shown using a selected group of components for the
bleeder control unit, there can be many alternatives,
modifications, and variations. For example, some of the components
may be expanded and/or combined. Other components may be inserted
to those noted above. Depending upon the embodiment, the
arrangement of components may be interchanged with others replaced.
Further details of these components are found throughout the
present specification.
[0089] In some embodiments, the comparator 631.sub.0 includes input
terminals 702 and 704 and an output terminal 706. As an example,
the input terminal 702 receives the sensing voltage 682 (e.g.,
V.sub.sense), and the input terminal 704 receives a threshold
voltage 790 (e.g., V.sub.th). For example, the threshold voltage
790 (e.g., V.sub.th) is smaller than the reference voltage 670
(e.g., V.sub.ref0) for the constant current unit 610. As an
example, the threshold voltage 790 (e.g., V.sub.th) is equal to the
threshold current (e.g., the holding current of the TRIAC dimmer
650) multiplied by the resistance (e.g., R.sub.1) of the resistor
662. In certain examples, if the sensing voltage 682 (e.g.,
V.sub.sense) is larger than the threshold voltage 790 (e.g.,
V.sub.th), the LED current 694 is larger than the threshold current
(e.g., the holding current of the TRIAC dimmer 650). In some
examples, if the sensing voltage 682 (e.g., V.sub.sense) is smaller
than the threshold voltage 790 (e.g., V.sub.th), the LED current
694 is smaller than the threshold current (e.g., the holding
current of the TRIAC dimmer 650).
[0090] In certain embodiments, the comparator 631.sub.0 compares
the sensing voltage 682 (e.g., V.sub.sense) and the threshold
voltage 790 (e.g., V.sub.th) and generates a comparison signal 792.
For example, if the sensing voltage 682 (e.g., V.sub.sense) is
larger than the threshold voltage 790 (e.g., V.sub.th), the
comparator 631.sub.0 generates the comparison signal 792 at a logic
high level. As an example, if the sensing voltage 682 (e.g.,
V.sub.sense) is smaller than the threshold voltage 790 (e.g.,
V.sub.th), the comparator 631.sub.0 generates the comparison signal
792 at a logic low level. In some embodiments, if the sensing
voltage 682 (e.g., V.sub.sense) changes from being smaller than the
threshold voltage 790 (e.g., V.sub.th) to being larger than the
threshold voltage 790 (e.g., V.sub.th), the comparison signal 792
changes from the logic low level to the logic high level. As an
example, the comparator 631.sub.0 outputs the comparison signal 792
at the output terminal 706.
[0091] According to certain embodiments, the comparison signal 792
is received by the delay sub-unit 632.sub.0, which in response
generates the control signal 684.sub.1. For example, if the
comparison signal 792 changes from the logic low level to the logic
high level, the delay sub-unit 632.sub.0, after a predetermined
delay (e.g., after t.sub.td1), changes the control signal 684.sub.1
from the logic low level to the logic high level. As an example, if
the comparison signal 792 changes from the logic high level to the
logic low level, the delay sub-unit 632.sub.0, without any
predetermined delay (e.g., without to), changes the control signal
684.sub.1 from the logic high level to the logic low level.
[0092] According to certain embodiments, the control signal
684.sub.1 is received by the delay sub-unit 633.sub.0, which in
response generates the control signal 684.sub.2. For example, if
the control signal 684.sub.1 changes from the logic low level to
the logic high level, the delay sub-unit 633.sub.0, after a
predetermined delay (e.g., after t.sub.d2), changes the control
signal 684.sub.2 from the logic high level to the logic low level.
As an example, if the control signal 684.sub.1 changes from the
logic high level to the logic low level, the delay sub-unit
633.sub.0, without any predetermined delay (e.g., without ta2),
changes the control signal 684.sub.2 from the logic low level to
the logic high level.
[0093] According to some embodiments, if the comparison signal 792
changes from the logic low level to the logic high level, the
control signal 684.sub.1, after a predetermined delay (e.g., after
tat), changes from the logic low level to the logic high level, and
the control signal 684.sub.2, after two predetermined delays (e.g.,
after both t.sub.d1 and t.sub.d2), changes from the logic high
level to the logic low level. According to certain embodiments, if
the comparison signal 792 changes from the logic high level to the
logic low level, the control signal 684.sub.1, without any
predetermined delay, changes from the logic high level to the logic
low level, and the control signal 684.sub.2, without any
predetermined delay, changes from the logic low level to the logic
high level.
[0094] As shown in FIG. 6, if the control signal 684.sub.1 is at
the logic high level, the switch 634.sub.1 is set to bias the
voltage 686 to the output voltage of the amplifier 632.sub.2, and
if the control signal 684.sub.1 is at the logic low level, the
switch 634.sub.1 is set to bias the voltage 686 to the reference
voltage 688.sub.1 (e.g., being larger than zero volts), according
to some embodiments. For example, if the control signal 684.sub.1
changes from the logic high level to the logic low level, the
voltage 686 changes from the output voltage of the amplifier
632.sub.2 to the reference voltage 688.sub.1 (e.g., being larger
than zero volts). As an example, if the control signal 684.sub.1
changes from the logic low level to the logic high level, the
voltage 686 changes from the reference voltage 688.sub.1 (e.g.,
being larger than zero volts) to the output voltage of the
amplifier 632.sub.2.
[0095] In certain embodiments, if the LED current 694, at a time of
change, changes from being lower than the threshold current to
being higher than the threshold current, the bleeder current 690,
after one predetermined delay (e.g., after t.sub.d1) from the time
of change, changes from the larger magnitude to the smaller
magnitude (e.g., the smaller magnitude that is larger than zero)
during the predetermined time duration, and after two predetermined
delays (e.g., after t.sub.d1 and t.sub.d2) from the time of change,
further changes from the smaller magnitude (e.g., the smaller
magnitude that is larger than zero) to zero during the
predetermined time duration. For example, the predetermined delay
t.sub.d1 is provided by the delay sub-unit 632.sub.0, and the
predetermined delay t.sub.d2 is provided by the delay sub-unit
633.sub.0. As an example, the falling edge of the control signal
684.sub.2 is delayed from the rising edge of the control signal
684.sub.1 by the predetermined delay t.sub.d2. For example, the
length of the predetermined time duration depends on the resistance
of the resistor 636 and the capacitance of the capacitor 638. In
some embodiments, if the LED current 694 changes from being higher
than the threshold current to being lower than the threshold
current, the bleeder current 690, without any predetermined delay
(e.g., without to and without td2), changes to a magnitude
according to Equation 5.
[0096] FIG. 8 shows simplified timing diagrams for the LED lighting
system 600 as shown in FIG. 6 according to certain embodiments of
the present invention. These diagrams are merely examples, which
should not unduly limit the scope of the claims. One of ordinary
skill in the art would recognize many variations, alternatives, and
modifications. The waveform 898 represents the rectified voltage
698 (e.g., VIN) as a function of time, the waveform 894 represents
the LED current 694 (e.g., I.sub.LED) as a function of time, the
waveform 884 represents the control signal 684.sub.1 (e.g.,
Ctr.sub.1) as a function of time, the waveform 885 represents the
control signal 684.sub.2 (e.g., Ctr.sub.2) as a function of time,
and the waveform 890 represents the bleeder current 690 (e.g.,
bleed) as a function of time.
[0097] In some embodiments, when the LED lighting system 600 works
properly, the TRIAC dimmer 650 clips parts of a waveform for the AC
input voltage 666 (e.g., VAC). As an example, from time to to time
ti, the rectified voltage 698 (e.g., VIN) is at a voltage level
that is close or equal to zero volts as shown by the waveform 898,
the LED current 694 (e.g., I.sub.LED) is equal to zero in magnitude
as shown by the waveform 894, the control signal 684.sub.1 (e.g.,
Ctr.sub.1) is at a logic low level as shown by the waveform 884,
the control signal 684.sub.2 (e.g., Ctr.sub.2) is at the logic high
level as shown by the waveform 885, and the bleeder current 690 is
allowed to be generated as shown by the waveform 890. As an
example, from time to to time ti, the bleeder current 690 is
allowed to be generated as shown by the waveform 890, so the
bleeder current 690 remains at zero and then increases in magnitude
as shown by the waveform 890.
[0098] As shown in FIG. 8, from time t.sub.1 to time t.sub.5, the
rectified voltage 698 (e.g., VIN) is at a high voltage level (e.g.,
a high voltage level that is not constant) as shown by the waveform
898, and the LED current 694 (e.g., I.sub.LED) is at a high current
level as shown by the waveform 894 according to some embodiments.
In certain examples, from time t.sub.1 to time t.sub.2, the control
signal 684.sub.1 (e.g., Ctr.sub.1) remains at the logic low level
as shown by the waveform 884, the control signal 684.sub.2 (e.g.,
Ctr.sub.2) remains at the logic high level as shown by the waveform
885, and the bleeder current 690 is at a current level 802 (e.g.,
being larger than zero) as shown by the waveform 890. For example,
the time duration from time t.sub.1 to time t.sub.2 is the
predetermined delay (e.g., to) provided by the delay sub-unit
632.sub.0.
[0099] In some examples, from time t.sub.2 to time t3, the control
signal 684.sub.1 (e.g., Ctr.sub.1) is at the logic high level as
shown by the waveform 884, the control signal 684.sub.2 (e.g.,
Ctr.sub.2) is at the logic high level as shown by the waveform 885,
and the bleeder current 690 changes from being equal to the current
level 802 (e.g., being larger than zero) to being equal to a
current level 804 (e.g., being larger than zero) gradually (e.g.,
slowly) during the predetermined time duration that starts at time
t.sub.2 as shown by the waveform 890. For example, the time
duration from time t.sub.2 to time t.sub.3 is the predetermined
delay (e.g., t.sub.d2) provided by the delay sub-unit 633.sub.0. As
an example, the time duration from time t.sub.2 to time t.sub.3 is
equal to the predetermined time duration, and the length of the
predetermined time duration depends on the resistance of the
resistor 336 and the capacitance of the capacitor 338.
[0100] In certain examples, from time t.sub.3 to time t.sub.4, the
control signal 684.sub.1 (e.g., Ctr.sub.1) is at the logic high
level as shown by the waveform 884, the control signal 684.sub.2
(e.g., Ctr.sub.2) is at the logic low level as shown by the
waveform 885, and the bleeder current 690 changes from being equal
to the current level 804 (e.g., being larger than zero) to being
equal to zero gradually (e.g., slowly) during the predetermined
time duration that starts at time t.sub.3 as shown by the waveform
890. As an example, the time duration from time t.sub.3 to time
t.sub.4 is equal to the predetermined time duration, and the length
of the predetermined time duration depends on the resistance of the
resistor 336 and the capacitance of the capacitor 338. In some
examples, from time t.sub.4 to time t.sub.5, the control signal
684.sub.1 (e.g., Ctr.sub.1) remains at the logic high level as
shown by the waveform 884, the control signal 684.sub.2 (e.g.,
Ctr.sub.2) remains at the logic low level as shown by the waveform
885, and the bleeder current 390 remains equal to zero.
[0101] As shown in FIG. 8, from time t.sub.3 to time t.sub.5, the
bleeder current 690 is not allowed to be generated as shown by the
waveform 890, so the bleeder current 690 changes from being equal
to the current level 804 (e.g., being larger than zero) to being
equal to zero gradually (e.g., slowly) from time t.sub.3 to time
t.sub.4 (e.g., during the predetermined time duration) and then the
bleeder current 690 remains equal to zero from time t.sub.4 to time
is according to certain embodiments.
[0102] From time is to time t6, the rectified voltage 698 (e.g.,
VIN) changes from the high voltage level to a low voltage level
(e.g., a low voltage level that is not constant but larger than
zero volts) as shown by the waveform 898, the LED current 694
(e.g., I.sub.LED) is equal to zero in magnitude as shown by the
waveform 894, the control signal 684.sub.1 (e.g., Ctr.sub.1) is at
the logic low level as shown by the waveform 884, the control
signal 684.sub.2 (e.g., Ctr.sub.2) is at the logic high level as
shown by the waveform 885, and the bleeder current 690 is allowed
to be generated as shown by the waveform 890, according to some
embodiments. For example, as shown by the waveform 890, the bleeder
current 690 increases but then becomes smaller with the decreasing
rectified voltage 698 (e.g., VIN) from time is to time t6.
[0103] As shown in FIG. 6, FIG. 7 and FIG. 8, two levels of control
mechanisms are used by the bleeder-current control sub-unit
622.sub.0 so that gradual (e.g., slow) reduction of the bleeder
current 690 is accomplished in two corresponding stages according
to certain embodiments. In some examples, the amplifier 632.sub.1
and the switch 634.sub.1, together with the resistor 636 and the
capacitor 638, are used to implement the first level of control
mechanism for the first stage, and the amplifier 632.sub.2 and the
switch 634.sub.2, together with the resistor 636 and the capacitor
638, are used to implement the second level of control mechanism
for the second stage. In certain example, the switch 634.sub.1 is
controlled by the control signal 684.sub.1 and the switch 634.sub.2
is controlled by the control signal 684.sub.2, so that the bleeder
current 690 becomes zero in two stages. For example, in the first
stage (e.g., from time t.sub.2 to time t.sub.3), the voltage 686
decreases from the reference voltage 688.sub.1 (e.g., V.sub.ref1)
to the reference voltage 688.sub.2 (e.g., V.sub.ref2) and the
bleeder current 690 decreases from the current level 802 as
determined by Equation 5 to the current level 804 as determined by
Equation 6. As an example, in the second stage (e.g., from time
t.sub.3 to time t.sub.4), the voltage 686 further decreases from
the reference voltage 688.sub.2 (e.g., V.sub.ref2) to the ground
voltage (e.g., zero volts) and the bleeder current 690 further
decreases from the current level 804 as determined by Equation 6 to
zero.
[0104] As discussed above and further emphasized here, FIG. 6, FIG.
7 and FIG. 8 are merely examples, which should not unduly limit the
scope of the claims. One of ordinary skill in the art would
recognize many variations, alternatives, and modifications. In some
embodiments, N levels of control mechanisms are used by the
bleeder-current control sub-unit 622.sub.0 so that gradual (e.g.,
slow) reduction of the bleeder current 690 is accomplished in N
corresponding stages, where N is an integer larger than 1. For
example, N is larger than 2. In certain examples, the change of a
control signal 684.sub.n occurs after a delay of tan from the time
when the change of a control signal 684.sub.n-1 occurs in response
to the LED current 694 (e.g., I.sub.LED) becomes larger than a
threshold current (e.g., the holding current of the TRIAC dimmer
650), where n is an integer larger than 1 but smaller than or equal
to N. As an example, the change of the control signal 684.sub.2
occurs after the delay of tae from the time when the change of the
control signal 684.sub.1 occurs in response to the LED current 694
(e.g., I.sub.LED) becomes larger than the threshold current (e.g.,
the holding current of the TRIAC dimmer 650). For example, the
change of the control signal 684.sub.3 occurs after a delay of to
from the time when the change of the control signal 684.sub.2
occurs in response to the LED current 694 (e.g., I.sub.LED) becomes
larger than the threshold current (e.g., the holding current of the
TRIAC dimmer 650). As an example, the change of the control signal
684.sub.N occurs after a delay of t.sub.dN from the time when the
change of the control signal 684.sub.N-1 occurs in response to the
LED current 694 (e.g., I.sub.LED) becomes larger than the threshold
current (e.g., the holding current of the TRIAC dimmer 650).
[0105] In certain embodiments, the bleeder-current control sub-unit
622.sub.0 includes amplifiers 632.sub.1, . . . , 632.sub.k, . . . ,
and 632.sub.N, switches 634.sub.1, . . . , 634.sub.k, . . . , and
634.sub.N, the resistor 636, and the capacitor 638, where k is an
integer larger than 1 but smaller than N. For example, a negative
input terminal of the amplifier 632.sub.k is coupled to an output
terminal of the amplifier 632.sub.k. As an example, the capacitor
638 is biased between the voltage 686 (e.g., V.sub.p) and the
ground voltage. In some examples, the positive input terminal of
the amplifier 632.sub.1 is biased to the reference voltage
688.sub.1 (e.g., V.sub.ref1). For example, the switch 634.sub.1 is
controlled by the control signal 684.sub.1 (e.g., Ctr.sub.1) so
that the voltage 686 (e.g., V.sub.p) either equals the reference
voltage 688.sub.1 (e.g., V.sub.ref1) to generate the bleeder
current 690 (e.g., I.sub.bleed) based at least in part on the
reference voltage 688.sub.1 (e.g., V.sub.ref1), or equals the
output voltage of the amplifier 632.sub.2 (e.g., through the
resistor 636) to generate the bleeder current 690 (e.g.,
I.sub.bleed) based at least in part on the output voltage of the
amplifier 632.sub.2. As an example, the switch 634.sub.2 is
controlled by the control signal 684.sub.2 (e.g., Ctr.sub.2) so
that the voltage 686 (e.g., V.sub.p) either equals the reference
voltage 688.sub.2 (e.g., V.sub.ref2) to generate the bleeder
current 690 (e.g., I.sub.bleed) based at least in part on the
reference voltage 688.sub.2 (e.g., V.sub.ref2), or equals the
output voltage of the amplifier 632.sub.3 to generate the bleeder
current 690 (e.g., I.sub.bleed) based at least in part on the
output voltage of the amplifier 632.sub.3. For example, the switch
634k is controlled by the control signal 684k (e.g., Ctr.sub.k) so
that the voltage 686 (e.g., V.sub.p) either equals the reference
voltage 688k (e.g., V.sub.refk) to generate the bleeder current 690
(e.g., I.sub.bleed) based at least in part on the reference voltage
688k (e.g., V.sub.refk), or equals the output voltage of the
amplifier 632.sub.k+1 to generate the bleeder current 690 (e.g.,
I.sub.bleed) based at least in part on the output voltage of the
amplifier 632.sub.k+1. As an example, the switch 634.sub.N is
controlled by the control signal 684.sub.N (e.g., Ctr.sub.N) so
that the voltage 686 (e.g., V.sub.p) either equals the reference
voltage 688.sub.N (e.g., V.sub.refN) to generate the bleeder
current 690 (e.g., I.sub.bleed) based at least in part on the
reference voltage 688.sub.N (e.g., V.sub.refN), or equals the
ground voltage (e.g., zero volts) to reduce the bleeder current 690
(e.g., bleed) to zero. In certain examples, the reference voltage
688.sub.j (e.g., V.sub.refj) is larger than zero volts but smaller
than the reference voltage 688.sub.j+1 (e.g., V.sub.ref(j+1)),
where j is an integer larger than 0 but smaller than N.
[0106] In some embodiments, the bleeder control unit 630 includes
the comparator 631.sub.0 and delay sub-units 6320.sub.1, . . .
6320.sub.m, . . . and 6320.sub.N, where N is an integer larger than
1 and m is an integer larger than 1 but smaller than N. For
example, the delay sub-unit 6320.sub.1 is the delay sub-unit 6320
as shown in FIG. 7. As an example, the delay sub-unit 6320.sub.2 is
the delay sub-unit 6330 as shown in FIG. 7. In certain examples,
the comparator 631.sub.0 compares the sensing voltage 682 (e.g.,
V.sub.sense) and the threshold voltage 790 (e.g., V.sub.th) and
generates the comparison signal 792. For example, the change of the
control signal 684.sub.1 occurs after a delay of to from the time
when the change of the comparison signal 792 in response to the
sensing voltage 682 (e.g., V.sub.sense) becoming larger than the
threshold voltage 790 (e.g., V.sub.th). As an example, the change
of the control signal 684.sub.m occurs after a delay of tam from
the time when the change of the control signal 684.sub.m-1 occurs
in response to the sensing voltage 682 (e.g., V.sub.sense) becoming
larger than the threshold voltage 790 (e.g., V.sub.th). For
example, the change of the control signal 684.sub.N occurs after a
delay of t.sub.dN from the time when the change of the control
signal 684.sub.N-1 occurs in response to the sensing voltage 682
(e.g., V.sub.sense) becoming larger than the threshold voltage 790
(e.g., V.sub.th). In some examples, the bleeder control unit 630
outputs the control signal 684.sub.1, . . . the control signal
684.sub.m, . . . and the control signal 684.sub.N to the
bleeder-current control sub-unit 6220. For example, the control
signal 684.sub.1, . . . the control signal 684.sub.m, . . . and the
control signal 684.sub.N are used to control the switch 634.sub.1,
. . . the switch 634.sub.m, . . . and the switch 634.sub.N.
[0107] FIG. 9 is a simplified circuit diagram showing an LED
lighting system according to some embodiments of the present
invention. This diagram is merely an example, which should not
unduly limit the scope of the claims. One of ordinary skill in the
art would recognize many variations, alternatives, and
modifications. As shown in FIG. 9, the LED lighting system 900
includes a TRIAC dimmer 950, a rectifying bridge 952 (e.g., a full
wave rectifying bridge), a fuse 954, one or more LEDs 942, and a
control system. As an example, the control system of the LED
lighting system 900 includes a constant current unit 910 (e.g., a
current regulator), a bleeder unit 920, a bleeder control unit 930,
and a voltage divider 940. Although the above has been shown using
a selected group of components for the LED lighting system, there
can be many alternatives, modifications, and variations. For
example, some of the components may be expanded and/or combined.
Other components may be inserted to those noted above. Depending
upon the embodiment, the arrangement of components may be
interchanged with others replaced. Further details of these
components are found throughout the present specification.
[0108] As shown in FIG. 9, the rectifying bridge 952 (e.g., a full
wave rectifying bridge) is coupled to the TRIAC dimmer 950 through
the fuse 954, and an AC input voltage 966 (e.g., VAC) is received
by the TRIAC dimmer 950 and is also rectified by the rectifying
bridge 952 to generate a rectified voltage 998 (e.g., VIN)
according to certain embodiments. As an example, the rectified
voltage 998 does not fall below the ground voltage (e.g., zero
volts).
[0109] According to some embodiments, the constant current unit 910
includes two terminals, one of which is coupled to the one or more
LEDs 942 and the other of which is coupled to the bleeder control
unit 930. As an example, the bleeder control unit 930 includes
three terminals, one of which is coupled to the constant current
unit 910, one of which is coupled to the bleeder unit 920, and the
other of which is coupled to the voltage divider 940. For example,
the bleeder unit 920 includes two terminals, one of which is
coupled to the bleeder control unit 930 and the other of which is
configured to receive the rectified voltage 998 (e.g., VIN). As an
example, the voltage divider 940 includes two terminals, one of
which is coupled to the bleeder control unit 930 and the other of
which is configured to receive the rectified voltage 998 (e.g.,
VIN).
[0110] According to certain embodiments, the bleeder control unit
930 is configured to detect a change of the rectified voltage 998
(e.g., VIN), to detect a phase range within which the TRIAC dimmer
950 is in the conduction state (e.g., on state), and to detect a
change of an LED current 994 (e.g., I.sub.LED) that flows through
the one or more LEDs 942. As an example, the bleeder control unit
930 is further configured to allow or not allow the bleeder unit
920 to generate a bleeder current 990 based at least in part on the
detected change of the rectified voltage 998 (e.g., VIN), the
detected phase range, and the detected change of the LED current
994.
[0111] According to some embodiments, the bleeder control unit 930
receives a voltage 976 from the voltage divider 940 and a sensing
voltage 982 (e.g., V.sub.sense) from the constant current unit 310,
and generates, based at least in part on the voltage 976 and the
sensing voltage 982, a control signal 984 to allow or not allow the
bleeder unit 920 to generate the bleeder current 990. As an
example, the voltage 976 represents the rectified voltage 998
(e.g., VIN), and the sensing voltage 982 represents the LED current
994 (e.g., I.sub.LED). For example, the voltage 976 is used to
detect a phase range within which the TRIAC dimmer 950 is in the
conduction state (e.g., on state) or a phase range within which the
TRIAC dimmer 950 is not in the conduction state (e.g., is in the
off state).
[0112] In certain embodiments, the constant current unit 910
includes a transistor 960, a resistor 962, and an amplifier 964.
For example, the amplifier 964 includes two input terminal and an
output terminal. As an example, one of the two input terminals
receives a reference voltage 970 (e.g., V.sub.ref0), and the other
of the two input terminals is coupled to the resistor 962 and
configured to generate the sensing voltage 982 (e.g., V.sub.sense).
For example, the sensing voltage 982 (e.g., V.sub.sense) is equal
to the LED current 994 (e.g., I.sub.LED) multiplied by the
resistance (e.g., R.sub.1) of the resistor 962.
[0113] In some embodiments, the voltage divider 940 includes
resistors 972 and 974. For example, the resistor 972 includes two
terminals, and the resistor 974 also includes two terminals. As an
example, one terminal of the resistor 972 receives the rectified
voltage 998 (e.g., VIN), the other terminal of the resistor 972 is
connected to one terminal of the resistor 974 and generates the
voltage 976, and the other terminal of the resistor 974 is biased
to the ground voltage (e.g., zero volts). For example, the voltage
976 is determined as follows:
V ls = R 5 R 4 + R 5 .times. V IN ( Equation 7 ) ##EQU00007##
[0114] where V.sub.Is represents the voltage 976, R.sub.4
represents the resistance value of the resistor 972, R.sub.5
represents the resistance value of the resistor 974, and V.sub.IN
represents the rectified voltage 998.
[0115] According to certain embodiments, if the voltage 976
indicates that the phase range within which the TRIAC dimmer 950 is
in the conduction state (e.g., on state) is smaller than a
predetermined conduction phase threshold, the bleeder control unit
930 generates the control signal 984 to allow or not allow the
bleeder unit 920 to generate the bleeder current 990 depending on
the comparison between the voltage 976 (e.g., V.sub.Is) and a
predetermined threshold voltage (e.g., V.sub.th1). For example, if
the voltage 976 indicates that the phase range within which the
TRIAC dimmer 950 is in the conduction state (e.g., on state) is
smaller than the predetermined conduction phase threshold, the
bleeder control unit 930 generates the control signal 984 to not
allow the bleeder unit 920 to generate the bleeder current 990 if
the voltage 976 (e.g., V.sub.Is) is larger than the predetermined
threshold voltage (e.g., V.sub.th1). As an example, if the voltage
976 indicates that the phase range within which the TRIAC dimmer
950 is in the conduction state (e.g., on state) is smaller than the
predetermined conduction phase threshold, the bleeder control unit
930 generates the control signal 984 to allow the bleeder unit 920
to generate the bleeder current 990 if the voltage 976 (e.g.,
V.sub.Is) is smaller than the predetermined threshold voltage
(e.g., V.sub.th1).
[0116] According to some embodiments, if the voltage 976 indicates
that the phase range within which the TRIAC dimmer 950 is in the
conduction state (e.g., on state) is larger than the predetermined
conduction phase threshold, the bleeder control unit 930 generates
the control signal 984 to allow or not allow the bleeder unit 920
to generate the bleeder current 990 depending on the comparison
between the sensing voltage 982 (e.g., V.sub.sense) and a
predetermined threshold voltage (e.g., V.sub.th2). In certain
examples, if the voltage 976 indicates that the phase range within
which the TRIAC dimmer 950 is in the conduction state (e.g., on
state) is larger than the predetermined conduction phase threshold,
the bleeder control unit 930 generates the control signal 984 to
not allow the bleeder unit 920 to generate the bleeder current 990
if the sensing voltage 982 (e.g., V.sub.sense) is larger than the
predetermined threshold voltage (e.g., V.sub.th2). For example, the
sensing voltage 982 (e.g., V.sub.sense) being larger than the
predetermined threshold voltage (e.g., V.sub.th2) represents the
LED current 994 being higher than a threshold current (e.g., a
holding current of the TRIAC dimmer 950). As an example, the
bleeder control unit 930 outputs the control signal 984 to the
bleeder unit 920, and the control signal 984 does not allow the
bleeder unit 920 to generate the bleeder current 990.
[0117] In some examples, if the voltage 976 indicates that the
phase range within which the TRIAC dimmer 950 is in the conduction
state (e.g., on state) is larger than the predetermined conduction
phase threshold, the bleeder control unit 930 generates the control
signal 984 to allow the bleeder unit 920 to generate the bleeder
current 990 if the sensing voltage 982 (e.g., V.sub.sense) is
smaller than the predetermined threshold voltage (e.g., V.sub.th2).
For example, the sensing voltage 982 (e.g., V.sub.sense) being
smaller than the predetermined threshold voltage (e.g., V.sub.th2)
represents the LED current 994 being lower than the threshold
current (e.g., a holding current of the TRIAC dimmer 950). As an
example, the bleeder control unit 930 outputs the control signal
984 to the bleeder unit 920, and the control signal 984 allows the
bleeder unit 920 to generate the bleeder current 990.
[0118] As shown in FIG. 9, the bleeder unit 920 receives the
control signal 984 from the bleeder control unit 930, and if the
control signal 984 allows the bleeder unit 920 to generate the
bleeder current 990, the bleeder unit 920 generates the bleeder
current 990 so that the TRIAC dimmer 950 can operate properly
according to certain embodiments.
[0119] In some examples, the bleeder unit 920 includes a
bleeder-current generation sub-unit 9210 and a bleeder-current
control sub-unit 9220. As an example, the bleeder-current
generation sub-unit 9210 includes an amplifier 922, a transistor
924, and a resistor 926. In certain examples, the bleeder-current
control sub-unit 9220 includes an amplifier 932, a switch 934, a
resistor 936, and a capacitor 938. For example, if the transistor
924 is in the saturation region, the bleeder current 990 is
determined as follows:
I bleed = V p R 2 ( Equation 8 ) ##EQU00008##
[0120] where I.sub.bleed represents the bleeder current 990,
V.sub.p represents a voltage 986 received by the amplifier 922, and
R.sub.2 represents the resistance value of the resistor 926.
[0121] In certain examples, the amplifier 922 includes a positive
input terminal (e.g., the "+" terminal) and a negative input
terminal (e.g., the "-" terminal). For example, the voltage 986 is
received by the positive input terminal of the amplifier 922. As an
example, the voltage 986 is controlled by the switch 934, which
makes the voltage 986 equal to either the ground voltage (e.g.,
zero volts) or a reference voltage 988 (e.g., V.sub.ref1). For
example, the reference voltage 988 is received by the amplifier 932
and is larger than zero volts.
[0122] According to some embodiments, if the voltage 976 indicates
that the phase range within which the TRIAC dimmer 950 is in the
conduction state (e.g., on state) is smaller than the predetermined
conduction phase threshold and the voltage 976 (e.g., V.sub.Is) is
smaller than the predetermined threshold voltage (e.g., V.sub.th1)
or if the voltage 976 indicates that the phase range within which
the TRIAC dimmer 950 is in the conduction state (e.g., on state) is
larger than the predetermined conduction phase threshold and the
sensing voltage 982 (e.g., V.sub.sense) is smaller than the
predetermined threshold voltage (e.g., V.sub.th2), the control
signal 984 received by the bleeder unit 920 sets the switch 934 so
that the positive input terminal (e.g., the "+" terminal) of the
amplifier 922 is biased to the reference voltage 988 through the
amplifier 932.
[0123] According to certain embodiments, if the voltage 976
indicates that the phase range within which the TRIAC dimmer 950 is
in the conduction state (e.g., on state) is smaller than the
predetermined conduction phase threshold and the voltage 976 (e.g.,
V.sub.Is) is larger than the predetermined threshold voltage (e.g.,
V.sub.th1) or if the voltage 976 indicates that the phase range
within which the TRIAC dimmer 950 is in the conduction state (e.g.,
on state) is larger than the predetermined conduction phase
threshold and the sensing voltage 982 (e.g., V.sub.sense) is larger
than the predetermined threshold voltage (e.g., V.sub.th2), the
control signal 984 received by the bleeder unit 920 sets the switch
934 so that the positive input terminal (e.g., the "+" terminal) of
the amplifier 922 is biased to the ground voltage through the
resistor 936.
[0124] In some embodiments, if the voltage 976 indicates that the
phase range within which the TRIAC dimmer 950 is in the conduction
state (e.g., on state) is larger than or equal to the predetermined
conduction phase threshold and the sensing voltage 982 (e.g.,
V.sub.sense) is smaller than the predetermined threshold voltage
(e.g., V.sub.th2), the control signal 984 received by the bleeder
unit 920 sets the switch 934 so that the positive input terminal
(e.g., the "+" terminal) of the amplifier 922 is biased to the
reference voltage 988 through the amplifier 932. In certain
embodiments, if the voltage 976 indicates that the phase range
within which the TRIAC dimmer 950 is in the conduction state (e.g.,
on state) is larger than or equal to the predetermined conduction
phase threshold and the sensing voltage 982 (e.g., V.sub.sense) is
larger than the predetermined threshold voltage (e.g., V.sub.th2),
the control signal 984 received by the bleeder unit 920 sets the
switch 934 so that the positive input terminal (e.g., the "+"
terminal) of the amplifier 922 is biased to the ground voltage
through the resistor 936.
[0125] According to certain embodiments, the control signal 984,
through the switch 934, changes the voltage 986 from being equal to
the reference voltage 988 (e.g., larger than zero volts) to being
equal to the ground voltage (e.g., equal to zero volts) so that the
bleeder current 990 changes from being larger than zero to being
equal to zero. As shown in FIG. 9, the resistor 936 and the
capacitor 938 are parts of an RC filtering circuit, which slows
down the decrease of the voltage 986 from the reference voltage 988
(e.g., larger than zero volts) to the ground voltage (e.g., equal
to zero volts) and also slows down the decrease of the bleeder
current 990 from being larger than zero to being equal to zero
according to some embodiments. For example, the bleeder unit 920 is
configured to turning off the bleeder current 990 gradually (e.g.,
slowly) during a predetermined time duration, and the length of the
predetermined time duration depends on the resistance of the
resistor 936 and the capacitance of the capacitor 938.
[0126] According to some embodiments, the control signal 984,
through the switch 934, changes the voltage 986 from being equal to
the ground voltage (e.g., equal to zero volts) to being equal to
the reference voltage 988 (e.g., larger than zero volts) so that
the bleeder current 990 changes from being equal to zero to being
larger than zero in order to for the TRIAC dimmer 950 to operate
properly. For example, when the voltage 986 is biased to the
reference voltage 988 (e.g., larger than zero volts), if the
transistor 924 is in the saturation region, the bleeder current 990
is determined as follows:
I bleed = V ref 1 R 2 ( Equation 9 ) ##EQU00009##
[0127] where I.sub.bleed represents the bleeder current 990,
V.sub.ref1 represents the reference voltage 988, and R.sub.2
represents the resistance value of the resistor 926.
[0128] FIG. 10 is a simplified circuit diagram showing the bleeder
control unit 930 of the LED lighting system 900 as shown in FIG. 9
according to certain embodiments of the present invention. This
diagram is merely an example, which should not unduly limit the
scope of the claims. One of ordinary skill in the art would
recognize many variations, alternatives, and modifications. As
shown in FIG. 10, the bleeder control unit 930 includes comparators
9310 and 9320, a delay sub-unit 9350, a conduction phase
determination sub-unit 9360 (e.g., a conduction phase detector),
and a switch 9370. Although the above has been shown using a
selected group of components for the bleeder control unit, there
can be many alternatives, modifications, and variations. For
example, some of the components may be expanded and/or combined.
Other components may be inserted to those noted above. Depending
upon the embodiment, the arrangement of components may be
interchanged with others replaced. Further details of these
components are found throughout the present specification.
[0129] In some embodiments, the comparator 9310 includes input
terminals 1002 and 1004 and an output terminal 1006. As an example,
the input terminal 1002 receives the voltage 976 (e.g., V.sub.Is),
and the input terminal 1004 receives a threshold voltage 1090
(e.g., V.sub.th1). In certain examples, if the voltage 976 (e.g.,
V.sub.Is) is larger than the threshold voltage 1090 (e.g.,
V.sub.th1), the TRIAC dimmer 950 is in the conduction state (e.g.,
on state). In some examples, if the voltage 976 (e.g., V.sub.Is) is
smaller than the threshold voltage 1090 (e.g., V.sub.th1), the
TRIAC dimmer 950 is not in the conduction state (e.g., is in the
off state).
[0130] In certain embodiments, the comparator 9310 compares the
voltage 976 (e.g., V.sub.Is) and the threshold voltage 1090 (e.g.,
V.sub.th1) and generates a comparison signal 1096. For example, if
the voltage 976 (e.g., V.sub.Is) is larger than the threshold
voltage 1090 (e.g., V.sub.th1), the comparator 9310 generates the
comparison signal 1096 at a logic high level. As an example, if the
voltage 976 (e.g., V.sub.Is) is smaller than the threshold voltage
1090 (e.g., V.sub.th1), the comparator 9310 generates the
comparison signal 1096 at a logic low level. In some embodiments,
if the voltage 976 (e.g., V.sub.Is) changes from being smaller than
the threshold voltage 1090 (e.g., V.sub.th1) to being larger than
the threshold voltage 1090 (e.g., V.sub.th1), the comparison signal
1096 changes from the logic low level to the logic high level. As
an example, the comparator 9310 outputs the comparison signal 1096
at the output terminal 1006.
[0131] According to some embodiments, the comparator 9320 includes
input terminals 1012 and 1014 and an output terminal 1016. As an
example, the input terminal 1012 receives the sensing voltage 982
(e.g., V.sub.sense), and the input terminal 1014 receives a
threshold voltage 1092 (e.g., V.sub.th2). For example, the
threshold voltage 1092 (e.g., V.sub.th2) is smaller than the
reference voltage 970 (e.g., V.sub.ref0) for the constant current
unit 910. As an example, the threshold voltage 1092 (e.g.,
V.sub.th2) is equal to the threshold current (e.g., the holding
current of the TRIAC dimmer 950) multiplied by the resistance
(e.g., R.sub.1) of the resistor 962. In certain examples, if the
sensing voltage 982 (e.g., V.sub.sense) is larger than the
threshold voltage 1092 (e.g., V.sub.th2), the LED current 994 is
larger than the threshold current (e.g., the holding current of the
TRIAC dimmer 950). In some examples, if the sensing voltage 982
(e.g., V.sub.sense) is smaller than the threshold voltage 1092
(e.g., V.sub.th2), the LED current 994 is smaller than the
threshold current (e.g., the holding current of the TRIAC dimmer
950).
[0132] According to certain embodiments, the comparator 9320
compares the sensing voltage 982 (e.g., V.sub.sense) and the
threshold voltage 1092 (e.g., V.sub.th2) and generates a comparison
signal 1082. For example, if the sensing voltage 982 (e.g.,
V.sub.sense) is larger than the threshold voltage 1092 (e.g.,
V.sub.th2), the comparator 9320 generates the comparison signal
1082 at a logic high level. As an example, if the sensing voltage
982 (e.g., V.sub.sense) is smaller than the threshold voltage 1092
(e.g., V.sub.th2), the comparator 9320 generates the comparison
signal 1082 at a logic low level. In some embodiments, if the
sensing voltage 982 (e.g., V.sub.sense) changes from being smaller
than the threshold voltage 1092 (e.g., W.sub.th2) to being larger
than the threshold voltage 1092 (e.g., V.sub.th2), the comparison
signal 1082 changes from the logic low level to the logic high
level. As an example, the comparator 9320 outputs the comparison
signal 1082 at the output terminal 1016.
[0133] As shown in FIG. 10, the conduction phase determination
sub-unit 9360 is configured to receive the comparison signal 1096
from the comparator 9310, compare a predetermined conduction phase
threshold and the phase range within which the TRIAC dimmer 950 is
in the conduction state (e.g., on state) or compare a predetermined
non-conduction phase threshold and the phase range within which the
TRIAC dimmer 950 is not in the conduction state (e.g., is in the
off state), and generate a detection signal 1080 based at least in
part on the comparison, according to some embodiments. For example,
the detection signal 1080 is received by the switch 9370, which
controls whether the comparison signal 1096 or the comparison
signal 1082 is received by the delay sub-unit 9350 as a signal
1084. In certain examples, if the phase range within which the
TRIAC dimmer 950 is in the conduction state (e.g., on state) is
smaller than the predetermined conduction phase threshold, the
comparison signal 1096 is received by the delay sub-unit 9350 as
the signal 1084. In some examples, if the phase range within which
the TRIAC dimmer 950 is in the conduction state (e.g., on state) is
larger than the predetermined conduction phase threshold, the
comparison signal 1082 is received by the delay sub-unit 9350 as
the signal 1084.
[0134] In certain embodiments, the conduction phase determination
sub-unit 9360 includes a duration determination component 9330
(e.g., a duration determination device) and a phase detection
component 9340 (e.g., a phase detection device). In some examples,
the duration determination component 9330 is configured to receive
a clock signal 1094 (e.g., CLK) and the comparison signal 1096, and
determine, within each cycle of the rectified voltage 998 (e.g.,
VIN), the time duration during which the comparison signal 1096
indicates that the voltage 976 (e.g., V.sub.Is) is smaller than the
threshold voltage 1090 (e.g., V.sub.th1) (e.g., during which the
TRIAC dimmer 950 is not in the conduction state), and the duration
determination component 9330 is further configured to generates a
signal 1098 representing the determined time duration. For example,
the signal 1098 is received by the phase detection component
9340.
[0135] In certain examples, the phase detection component 9340 is
configured to receive the signal 1098 representing the determined
time duration, determine whether the determined duration is larger
than a predetermined duration threshold, and generates the
detection signal 1080 based on at least the determined duration and
the predetermined duration threshold. For example, the detection
signal 1080 is received by the switch 9370. As an example, if the
detection signal 1080 indicates that the determined duration is
larger than the predetermined duration threshold, the switch 9370
sets the comparison signal 1096 to be the signal 1084 that is
received by the delay sub-unit 9350. For example, if the detection
signal 1080 indicates that the determined duration is smaller than
the predetermined duration threshold, the switch 9370 sets the
comparison signal 1082 to be the signal 1084 that is received by
the delay sub-unit 9350.
[0136] According to certain embodiments, within each cycle of the
rectified voltage 998 (e.g., VIN), the time duration during which
the voltage 976 (e.g., V.sub.Is) is smaller than the threshold
voltage 1090 (e.g., V.sub.th1) corresponds to the phase range
within which the TRIAC dimmer 950 is not in the conduction state
(e.g., is in the off state). According to some embodiments, within
each cycle of the rectified voltage 998 (e.g., VIN), the time
duration during which the voltage 976 (e.g., V.sub.Is) is larger
than the threshold voltage 1090 (e.g., V.sub.th1) corresponds to
the phase range within which the TRIAC dimmer 950 is in the
conduction state (e.g., on state).
[0137] In some embodiments, the phase range within which the TRIAC
dimmer 950 is in the conduction state (e.g., on state) being
smaller than the predetermined conduction phase threshold
corresponds to the phase range within which the TRIAC dimmer 950 is
not in the conduction state (e.g., is in the off state) being
larger than the predetermined non-conduction phase threshold. In
certain embodiments, the phase range within which the TRIAC dimmer
950 is in the conduction state (e.g., on state) being larger than
the predetermined conduction phase threshold corresponds to the
phase range within which the TRIAC dimmer 950 is not in the
conduction state (e.g., is in the off state) being smaller than the
predetermined non-conduction phase threshold.
[0138] According to certain embodiments, the comparison signal 1084
is received by the delay sub-unit 9350, which in response generates
the control signal 1084. For example, if the signal 1084 changes
from the logic low level to the logic high level, the delay
sub-unit 9350, after a predetermined delay (e.g., after t.sub.d),
changes the control signal 984 from the logic low level to the
logic high level. As an example, if the signal 1084 changes from
the logic high level to the logic low level, the delay sub-unit
9350, without any predetermined delay (e.g., without t.sub.d),
changes the control signal 984 from the logic high level to the
logic low level.
[0139] As shown in FIG. 9, if the control signal 984 is at the
logic high level, the switch 934 is set to bias the voltage 986 to
the ground voltage (e.g., being equal to zero volts), and if the
control signal 984 is at the logic low level, the switch 934 is set
to bias the voltage 986 to the reference voltage 988 (e.g., being
larger than zero volts), according to some embodiments. For
example, if the control signal 984 changes from the logic high
level to the logic low level, the voltage 986 changes from the
ground voltage (e.g., being equal to zero volts) to the reference
voltage 988 (e.g., being larger than zero volts). As an example, if
the control signal 984 changes from the logic low level to the
logic high level, the voltage 986 changes from the reference
voltage 988 (e.g., being larger than zero volts) to the ground
voltage (e.g., being equal to zero volts).
[0140] In certain embodiments, if the voltage 976 indicates that
the phase range within which the TRIAC dimmer 950 is in the
conduction state (e.g., on state) is smaller than the predetermined
conduction phase threshold and the voltage 976 (e.g., V.sub.Is)
changes from being smaller than the predetermined threshold voltage
(e.g., V.sub.th1) to being larger than the predetermined threshold
voltage (e.g., V.sub.th1) or if the voltage 976 indicates that the
phase range within which the TRIAC dimmer 950 is in the conduction
state (e.g., on state) is larger than the predetermined conduction
phase threshold and the sensing voltage 982 (e.g., V.sub.sense)
changes from being smaller than the predetermined threshold voltage
(e.g., V.sub.th2) to being larger than the predetermined threshold
voltage (e.g., V.sub.th2), the bleeder current 990, after the
predetermined delay (e.g., after t.sub.d), changes gradually (e.g.,
slowly) from being larger than zero to being equal to zero during
the predetermined time duration. For example, the predetermined
delay (e.g., t.sub.d) is provided by the delay sub-unit 9350. As an
example, the length of the predetermined time duration depends on
the resistance of the resistor 936 and the capacitance of the
capacitor 938.
[0141] In some embodiments, if the voltage 976 indicates that the
phase range within which the TRIAC dimmer 950 is in the conduction
state (e.g., on state) is smaller than the predetermined conduction
phase threshold and the voltage 976 (e.g., V.sub.Is) changes from
being larger than the predetermined threshold voltage (e.g.,
V.sub.th1) to being smaller than the predetermined threshold
voltage (e.g., V.sub.th1) or if the voltage 976 indicates that the
phase range within which the TRIAC dimmer 950 is in the conduction
state (e.g., on state) is larger than the predetermined conduction
phase threshold and the sensing voltage 982 (e.g., V.sub.sense)
changes from being larger than the predetermined threshold voltage
(e.g., V.sub.th2) to being smaller than the predetermined threshold
voltage (e.g., V.sub.th2), the bleeder current 990, without any
predetermined delay (e.g., without t.sub.d), changes from being
equal to zero to being larger than zero.
[0142] FIG. 11 shows simplified timing diagrams for the LED
lighting system 900 as shown in FIG. 9 if the phase range within
which the TRIAC dimmer 950 is in the conduction state is smaller
than the predetermined conduction phase threshold according to
certain embodiments of the present invention. These diagrams are
merely examples, which should not unduly limit the scope of the
claims. One of ordinary skill in the art would recognize many
variations, alternatives, and modifications. For example, the
waveform 1198 represents the rectified voltage 998 (e.g., VIN) as a
function of time if the phase range within which the TRIAC dimmer
950 is in the conduction state (e.g., on state) is smaller than the
predetermined conduction phase threshold, the waveform 1194
represents the LED current 994 (e.g., I.sub.LED) as a function of
time if the phase range within which the TRIAC dimmer 950 is in the
conduction state (e.g., on state) is smaller than the predetermined
conduction phase threshold, the waveform 1186 represents the
voltage 986 (e.g., V.sub.p) as a function of time if the phase
range within which the TRIAC dimmer 950 is in the conduction state
(e.g., on state) is smaller than the predetermined conduction phase
threshold, and the waveform 1190 represents the bleeder current 990
(e.g., I.sub.bleed) as a function of time if the phase range within
which the TRIAC dimmer 950 is in the conduction state (e.g., on
state) is smaller than the predetermined conduction phase
threshold.
[0143] In some embodiments, when the LED lighting system 900 works
properly, the TRIAC dimmer 950 clips parts of a waveform for the AC
input voltage 966 (e.g., VAC). In certain examples, from time to to
time ti, the rectified voltage 998 (e.g., VIN) is at a voltage
level that is close or equal to zero volts and is smaller than a
threshold voltage 1102, as shown by the waveform 1198, indicating
that the voltage 976 (e.g., V.sub.Is) is also smaller than the
predetermined threshold voltage (e.g., V.sub.th1). For example, the
predetermined threshold voltage (e.g., V.sub.th1) for the voltage
976 (e.g., V.sub.Is) has the following relationship with the
threshold voltage 1102 for the rectified voltage 998 (e.g.,
VIN):
V th 1 = R 5 R 4 + R 5 .times. V th_IN ( Equation 10 )
##EQU00010##
[0144] where V.sub.th1 represents the predetermined threshold
voltage for the voltage 976 (e.g., V.sub.Is), R.sub.4 represents
the resistance value of the resistor 972, R.sub.5 represents the
resistance value of the resistor 974, and V.sub.th_IN represents
the threshold voltage 1102 for the rectified voltage 998 (e.g.,
VIN).
[0145] In some embodiments, at time ti, the rectified voltage 998
(e.g., VIN) changes from being smaller than the threshold voltage
1102 to being larger than the threshold voltage 1102, as shown by
the waveform 1198, indicating that the voltage 976 (e.g., V.sub.Is)
changes from being smaller than the predetermined threshold voltage
(e.g., V.sub.th1) to being larger than the predetermined threshold
voltage (e.g., V.sub.th1). In certain embodiments, from time
t.sub.1 to time t.sub.4, the rectified voltage 998 (e.g., VIN)
remains larger than the threshold voltage 1102, as shown by the
waveform 1198, indicating that the voltage 976 (e.g., V.sub.Is)
also remains larger than the predetermined threshold voltage (e.g.,
V.sub.th1).
[0146] According to some embodiments, at time t4, the rectified
voltage 998 (e.g., VIN) changes from being larger than the
threshold voltage 1102 to being smaller than the threshold voltage
1102, as shown by the waveform 1198, indicating that the voltage
976 (e.g., V.sub.Is) also changes from being larger than the
predetermined threshold voltage (e.g., V.sub.th1) to being smaller
than the predetermined threshold voltage (e.g., V.sub.th1).
According to certain embodiments, from time t.sub.4 to time
t.sub.5, the rectified voltage 998 (e.g., VIN) remains smaller than
the threshold voltage 1102, as shown by the waveform 1198,
indicating that the voltage 976 (e.g., V.sub.Is) also remains
smaller than the predetermined threshold voltage (e.g.,
V.sub.th1).
[0147] In some embodiments, at time t.sub.5, the rectified voltage
998 (e.g., VIN) reaches the voltage level that is close or equal to
zero volts and is smaller than the threshold voltage 1102, as shown
by the waveform 1198, indicating that the voltage 976 (e.g.,
V.sub.Is) also reaches the voltage level that is close or equal to
zero volts and is smaller than the predetermined threshold voltage
(e.g., V.sub.th1). In certain embodiments, from time t.sub.5 to
time t.sub.6, similar to from time t.sub.0 time t.sub.1, the
rectified voltage 998 (e.g., VIN) remains at the voltage level that
is close or equal to zero volts and is smaller than the threshold
voltage 1102, as shown by the waveform 1198, indicating that the
voltage 976 (e.g., V.sub.Is) also remains smaller than the
predetermined threshold voltage (e.g., V.sub.th1).
[0148] As shown in FIG. 11, from time to to time ti, the LED
current 994 (e.g., I.sub.LED) is equal to zero in magnitude as
shown by the waveform 1194, the voltage 986 (e.g., V.sub.p) is
equal to the reference voltage 988 and larger than zero in
magnitude as shown by the waveform 1186, and the bleeder current
990 is allowed to be generated as shown by the waveform 1190,
according to some embodiments. As an example, from time to to time
ti, the bleeder current 990 is allowed to be generated as shown by
the waveform 1190, so the bleeder current 990 remains at zero and
then increases in magnitude to a high current level (e.g., being
larger than zero) as shown by the waveform 1190.
[0149] According to certain embodiments, at time ti, the LED
current 994 (e.g., I.sub.LED) changes from zero to a high current
level as shown by the waveform 1194. According to some embodiments,
from time t.sub.1 to time t.sub.2, the LED current 994 (e.g.,
I.sub.LED) remains at the high current level as shown by the
waveform 1194, the voltage 986 (e.g., V.sub.p) remains equal to the
reference voltage 988 and larger than zero in magnitude as shown by
the waveform 1186, and the bleeder current 990 is at the high
current level (e.g., being larger than zero) as shown by the
waveform 1190. For example, the time duration from time t.sub.1 to
time t.sub.2 is the predetermined delay (e.g., t.sub.d) provided by
the delay sub-unit 9350.
[0150] In some embodiments, from time t.sub.2 to time t3, the LED
current 994 (e.g., I.sub.LED) remains at the high current level as
shown by the waveform 1194, the voltage 986 (e.g., V.sub.p) changes
from being equal to the reference voltage 988 (e.g., larger than
zero volts) to being equal to the ground voltage (e.g., equal to
zero volts) gradually (e.g., slowly) during the predetermined time
duration as shown by the waveform 1186, and the bleeder current 990
also changes from being equal to the high current level (e.g.,
being larger than zero) to being equal to zero gradually (e.g.,
slowly) during the predetermined time duration as shown by the
waveform 1190. As an example, the time duration from time t.sub.2
to time t.sub.3 is equal to the predetermined time duration, and
the length of the predetermined time duration depends on the
resistance of the resistor 936 and the capacitance of the capacitor
938. In certain embodiments, from time t.sub.3 to time t4, the LED
current 994 (e.g., I.sub.LED) changes from the high current level
to zero as shown by the waveform 1194, the voltage 986 (e.g.,
V.sub.p) remains equal to the ground voltage (e.g., equal to zero
volts) as shown by the waveform 1186, and the bleeder current 990
also remains equal to zero as shown by the waveform 1190.
[0151] As shown in FIG. 11, from time t.sub.2 to time t.sub.4, the
bleeder current 990 is not allowed to be generated as shown by the
waveform 1190, so the bleeder current 990 changes from being equal
to the high current level (e.g., being larger than zero) to being
equal to zero gradually (e.g., slowly) from time t.sub.2 to time
t.sub.3 (e.g., during the predetermined time duration) and then the
bleeder current 990 remains equal to zero from time t.sub.3 to time
t.sub.4 according to certain embodiments.
[0152] According to some embodiments, at time t4, the voltage 986
(e.g., V.sub.p) changes from being equal to the ground voltage
(e.g., being equal to zero volts) to being equal to the reference
voltage 988 (e.g., larger than zero volts) as shown by the waveform
1186. According to certain embodiments, from time t.sub.4 to time
t.sub.5, the LED current 994 (e.g., I.sub.LED) is equal to zero in
magnitude as shown by the waveform 1194, the voltage 986 (e.g.,
V.sub.p) remains equal to the reference voltage 988 (e.g., larger
than zero volts) as shown by the waveform 1186, and the bleeder
current 990 is allowed to be generated as shown by the waveform
1190. For example, from time t.sub.4 to time t.sub.5, the bleeder
current 990 increases but then becomes smaller with the decreasing
rectified voltage 998 (e.g., VIN), as shown by the waveform
1190.
[0153] According to certain embodiments, from time is to time t6,
similar to from time to to time ti, the LED current 994 (e.g.,
I.sub.LED) is equal to zero in magnitude as shown by the waveform
1194, the voltage 986 (e.g., V.sub.p) remains equal to the
reference voltage 988 and larger than zero in magnitude as shown by
the waveform 1186, and the bleeder current 990 is allowed to be
generated as shown by the waveform 1190. As an example, from time
is to time t.sub.6, the bleeder current 990 is allowed to be
generated as shown by the waveform 1190, so the bleeder current 990
remains at zero and then increases in magnitude to the high current
level (e.g., being larger than zero) as shown by the waveform
1190.
[0154] As shown in FIG. 9 and FIG. 10, the LED lighting system 900
provides the RC filtering circuit that includes the resistor 936
and the capacitor 938 in order to control how fast the bleeder
current 990 changes from being equal to the high current level
(e.g., being larger than zero) to being equal to zero according to
certain embodiments. In some examples, the bleeder current 990
changes from being equal to the high current level (e.g., being
larger than zero) to being equal to zero gradually (e.g., slowly)
during the predetermined time duration, and the length of the
predetermined time duration depends on the resistance of the
resistor 936 and the capacitance of the capacitor 938.
[0155] In certain examples, if the voltage 976 indicates that the
phase range within which the TRIAC dimmer 950 is in the conduction
state (e.g., on state) is smaller than the predetermined conduction
phase threshold, the LED lighting system 900 uses the delay
sub-unit 9350 as part of the bleeder control unit 930 in order to
cause the predetermined delay (e.g., t.sub.d) after the voltage 976
(e.g., V.sub.Is) becomes larger than the predetermined threshold
voltage (e.g., V.sub.th1) but before the voltage 986 starts
decreasing from the reference voltage 988 and the bleeder current
990 also starts decreasing from the high current level (e.g., being
larger than zero). In some examples, if the voltage 976 indicates
that the phase range within which the TRIAC dimmer 950 is in the
conduction state (e.g., on state) is larger than the predetermined
conduction phase threshold, the LED lighting system 900 uses the
delay sub-unit 9350 as part of the bleeder control unit 930 in
order to cause the predetermined delay (e.g., t.sub.d) after the
sensing voltage 982 (e.g., V.sub.sense) becomes larger than the
predetermined threshold voltage (e.g., V.sub.th2) but before the
voltage 986 starts decreasing from the reference voltage 988 and
the bleeder current 990 also starts decreasing from the high
current level (e.g., being larger than zero).
[0156] According to some embodiments, the predetermined delay
(e.g., t.sub.d) helps to stabilize the conduction state (e.g., on
state) of the TRIAC dimmer 950. According to certain embodiments,
the gradual (e.g., slow) reduction of the bleeder current 990
during the predetermined time duration helps to reduce (e.g.,
eliminate) the oscillation of the rectified voltage 998 (e.g., VIN)
and also helps to stabilize the LED current 994 (e.g., I.sub.LED)
to reduce (e.g., eliminate) blinking of the one or more LEDs
942.
[0157] As shown in FIG. 11, the time duration from time t.sub.1 to
time t.sub.5 (e.g., time duration T.sub.on) corresponds to the
phase range within which the TRIAC dimmer 950 is in the conduction
state (e.g., on state), and the time duration from time is to time
t6 (e.g., time duration T.sub.off) corresponds to the phase range
within which the TRIAC dimmer 950 is not in the conduction state
(e.g., is in the off state), according to certain embodiments. In
some examples, referring to Equation 10, the bleeder control unit
930 uses the threshold voltage 1090 (e.g., V.sub.th1) to determine
the time when the TRIAC dimmer 950 changes from the conduction
state (e.g., on state) to the non-conduction state (e.g., off
state). For example, the threshold voltage 1090 (e.g., V.sub.th1)
is larger than zero volts, so time t.sub.4 is different from time
t.sub.5. As an example, for the bleeder control unit 930, the time
duration from time t.sub.1 to time t.sub.4 is determined to
represent the phase range within which the TRIAC dimmer 950 is in
the conduction state (e.g., on state), and the time duration from
time t.sub.4 to time t6 is determined to represent the phase range
within which the TRIAC dimmer 950 is not in the conduction state
(e.g., is in the off state).
[0158] In certain embodiments, the LED lighting system 900 as shown
in FIGS. 9, 10, and 11 provides one or more advantages. For
example, if the phase range within which the TRIAC dimmer 950 is in
the conduction state (e.g., on state) is so small that the TRIAC
dimmer 950 is in the conduction state (e.g., on state) only when
the rectified voltage 998 (e.g., VIN) is small and the sensing
voltage 982 (e.g., V.sub.sense) is smaller than the threshold
voltage 1092 (e.g., V.sub.th2), the LED lighting system 900 does
not allow the bleeder current 990 to be generated when the
rectified voltage 998 (e.g., VIN) is larger than the threshold
voltage 1102. As an example, if the phase range within which the
TRIAC dimmer 950 is in the conduction state (e.g., on state) is
smaller than the predetermined conduction phase threshold, the LED
lighting system 900 allows or does not allow the bleeder current
990 to be generated based on the comparison between the voltage 976
(e.g., V.sub.Is) and the threshold voltage 1090 (e.g., V.sub.th1),
in order to stabilize the conduction state (e.g., on state) of the
TRIAC dimmer 950, stabilize the LED current 994 (e.g., I.sub.LED),
and/or reduce (e.g., eliminate) blinking of the one or more LEDs
942.
[0159] FIG. 12 is a simplified circuit diagram showing an LED
lighting system according to certain embodiments of the present
invention. This diagram is merely an example, which should not
unduly limit the scope of the claims. One of ordinary skill in the
art would recognize many variations, alternatives, and
modifications. As shown in FIG. 12, the LED lighting system 1200
includes a TRIAC dimmer 1250, a rectifying bridge 1252 (e.g., a
full wave rectifying bridge), a fuse 1254, one or more LEDs 1242,
and a control system. As an example, the control system of the LED
lighting system 1200 includes a constant current unit 1210 (e.g., a
current regulator), a bleeder unit 1220, a bleeder control unit
1230, and a voltage divider 1240. Although the above has been shown
using a selected group of components for the LED lighting system,
there can be many alternatives, modifications, and variations. For
example, some of the components may be expanded and/or combined.
Other components may be inserted to those noted above. Depending
upon the embodiment, the arrangement of components may be
interchanged with others replaced. Further details of these
components are found throughout the present specification.
[0160] As shown in FIG. 12, the rectifying bridge 1252 (e.g., a
full wave rectifying bridge) is coupled to the TRIAC dimmer 1250
through the fuse 1254, and an AC input voltage 1266 (e.g., VAC) is
received by the TRIAC dimmer 1250 and is also rectified by the
rectifying bridge 1252 to generate a rectified voltage 1298 (e.g.,
VIN) according to certain embodiments. As an example, the rectified
voltage 1298 does not fall below the ground voltage (e.g., zero
volts).
[0161] According to some embodiments, the constant current unit
1210 includes two terminals, one of which is coupled to the one or
more LEDs 1242 and the other of which is coupled to the bleeder
control unit 1230. As an example, the bleeder control unit 1230
includes three terminals, one of which is coupled to the constant
current unit 1210, one of which is coupled to the bleeder unit
1220, and the other of which is coupled to the voltage divider
1240. For example, the bleeder unit 1220 includes two terminals,
one of which is coupled to the bleeder control unit 1230 and the
other of which is configured to receive the rectified voltage 1298
(e.g., VIN).
[0162] According to certain embodiments, the bleeder control unit
1230 is configured to detect a change of the rectified voltage 1298
(e.g., VIN), to detect a phase range within which the TRIAC dimmer
1250 is in the conduction state (e.g., on state), and to detect a
change of an LED current 1294 (e.g., I.sub.LED) that flows through
the one or more LEDs 1242. As an example, the bleeder control unit
1230 is further configured to allow or not allow the bleeder unit
1220 to generate a bleeder current 1290 based at least in part on
the detected change of the rectified voltage 1298 (e.g., VIN), the
detected phase range, and the detected change of the LED current
1294.
[0163] According to some embodiments, the bleeder control unit 1230
receives a voltage 1276 from the voltage divider 1240 and a sensing
voltage 1282 (e.g., V.sub.sense) from the constant current unit
1210, and generates, based at least in part on the voltage 1276 and
the sensing voltage 1282, control signals 1284.sub.1 and 1284.sub.2
to allow or not allow the bleeder unit 1220 to generate the bleeder
current 1290. As an example, the voltage 1276 represents the
rectified voltage 1298 (e.g., VIN), and the sensing voltage 1282
represents the LED current 1294 (e.g., I.sub.LED). For example, the
voltage 1276 is used to detect a phase range within which the TRIAC
dimmer 1250 is in the conduction state (e.g., on state) or a phase
range within which the TRIAC dimmer 1250 is not in the conduction
state (e.g., is in the off state).
[0164] In some embodiments, the constant current unit 1210 includes
a transistor 1260, a resistor 1262, and an amplifier 1264. For
example, the amplifier 1264 includes two input terminal and an
output terminal. As an example, one of the two input terminals
receives a reference voltage 1270 (e.g., V.sub.ref0), and the other
of the two input terminals is coupled to the resistor 1262 and
configured to generate the sensing voltage 1282 (e.g.,
V.sub.sense). For example, the sensing voltage 1282 (e.g.,
V.sub.sense) is equal to the LED current 1294 (e.g., I.sub.LED)
multiplied by the resistance (e.g., R.sub.1) of the resistor
1262.
[0165] In certain embodiments, the voltage divider 1240 includes
resistors 1272 and 1274. For example, the resistor 1272 includes
two terminals, and the resistor 1274 also includes two terminals.
As an example, one terminal of the resistor 1272 receives the
rectified voltage 1298 (e.g., VIN), the other terminal of the
resistor 1272 is connected to one terminal of the resistor 1274 and
generates the voltage 1276, and the other terminal of the resistor
1274 is biased to the ground voltage (e.g., zero volts). For
example, the voltage 1276 is determined as follows:
V ls = R 5 R 4 + R 5 .times. V IN ( Equation 11 ) ##EQU00011##
[0166] where V.sub.Is represents the voltage 1276, R.sub.4
represents the resistance value of the resistor 1272, R.sub.5
represents the resistance value of the resistor 1274, and V.sub.IN
represents the rectified voltage 1298.
[0167] According to certain embodiments, if the voltage 1276
indicates that the phase range within which the TRIAC dimmer 1250
is in the conduction state (e.g., on state) is smaller than a
predetermined conduction phase threshold, the bleeder control unit
1230 generates the control signals 1284.sub.1 and 1284.sub.2 to
allow or not allow the bleeder unit 1220 to generate the bleeder
current 1290 depending on the comparison between the voltage 1276
(e.g., V.sub.Is) and a predetermined threshold voltage (e.g.,
V.sub.th1). For example, if the voltage 1276 indicates that the
phase range within which the TRIAC dimmer 1250 is in the conduction
state (e.g., on state) is smaller than the predetermined conduction
phase threshold, the bleeder control unit 1230 generates the
control signals 1284.sub.1 and 1284.sub.2 to not allow the bleeder
unit 1220 to generate the bleeder current 1290 if the voltage 1276
(e.g., V.sub.Is) is larger than the predetermined threshold voltage
(e.g., V.sub.th1). As an example, if the voltage 1276 indicates
that the phase range within which the TRIAC dimmer 1250 is in the
conduction state (e.g., on state) is smaller than the predetermined
conduction phase threshold, the bleeder control unit 1230 generates
the control signals 1284.sub.1 and 1284.sub.2 to allow the bleeder
unit 1220 to generate the bleeder current 1290 if the voltage 1276
(e.g., V.sub.Is) is smaller than the predetermined threshold
voltage (e.g., V.sub.th1).
[0168] According to some embodiments, if the voltage 1276 indicates
that the phase range within which the TRIAC dimmer 1250 is in the
conduction state (e.g., on state) is larger than the predetermined
conduction phase threshold, the bleeder control unit 1230 generates
the control signals 1284.sub.1 and 1284.sub.2 to allow or not allow
the bleeder unit 1220 to generate the bleeder current 1290
depending on the comparison between the sensing voltage 1282 (e.g.,
V.sub.sense) and a predetermined threshold voltage (e.g.,
V.sub.th2). In certain examples, if the voltage 1276 indicates that
the phase range within which the TRIAC dimmer 1250 is in the
conduction state (e.g., on state) is larger than the predetermined
conduction phase threshold, the bleeder control unit 1230 generates
the control signals 1284.sub.1 and 1284.sub.2 to not allow the
bleeder unit 1220 to generate the bleeder current 1290 if the
sensing voltage 1282 (e.g., V.sub.sense) is larger than the
predetermined threshold voltage (e.g., V.sub.th2). For example, the
sensing voltage 1282 (e.g., V.sub.sense) being larger than the
predetermined threshold voltage (e.g., V.sub.th2) represents the
LED current 1294 being higher than a threshold current (e.g., a
holding current of the TRIAC dimmer 1250). As an example, the
bleeder control unit 1230 outputs the control signals 1284.sub.1
and 1284.sub.2 to the bleeder unit 1220, and the control signals
1284.sub.1 and 1284.sub.2 do not allow the bleeder unit 1220 to
generate the bleeder current 1290.
[0169] In some examples, if the voltage 1276 indicates that the
phase range within which the TRIAC dimmer 1250 is in the conduction
state (e.g., on state) is larger than the predetermined conduction
phase threshold, the bleeder control unit 1230 generates the
control signals 1284.sub.1 and 1284.sub.2 to allow the bleeder unit
1220 to generate the bleeder current 1290 if the sensing voltage
1282 (e.g., V.sub.sense) is smaller than the predetermined
threshold voltage (e.g., V.sub.th2). For example, the sensing
voltage 1282 (e.g., V.sub.sense) being smaller than the
predetermined threshold voltage (e.g., Vtn2) represents the LED
current 1294 being lower than the threshold current (e.g., a
holding current of the TRIAC dimmer 1250). As an example, the
bleeder control unit 1230 outputs the control signals 1284.sub.1
and 1284.sub.2 to the bleeder unit 1220, and the control signals
1284.sub.1 and 1284.sub.2 allow the bleeder unit 1220 to generate
the bleeder current 1290.
[0170] In certain embodiments, if the sensing voltage 1282 (e.g.,
V.sub.sense) indicates that the LED current 1294 is higher than a
threshold current (e.g., a holding current of the TRIAC dimmer
1250), the bleeder control unit 1230 outputs the control signals
1284.sub.1 and 1284.sub.2 to the bleeder unit 1220, and the control
signals 1284.sub.1 and 1284.sub.2 do not allow the bleeder unit
1220 to generate the bleeder current 1290. In some embodiments, if
the sensing voltage 1282 indicates that the LED current 1294 is
lower than the threshold current (e.g., a holding current of the
TRIAC dimmer 1250), the bleeder control unit 1230 outputs the
control signals 1284.sub.1 and 1284.sub.2 to the bleeder unit 1220,
and the control signals 1284.sub.1 and 1284.sub.2 allow the bleeder
unit 1220 to generate the bleeder current 1290. As an example, the
bleeder unit 1220 receives the control signals 1284.sub.1 and
1284.sub.2 from the bleeder control unit 1230, and if the control
signals 1284.sub.1 and 1284.sub.2 allow the bleeder unit 1220 to
generate the bleeder current 1290, the bleeder unit 1220 generates
the bleeder current 1290 so that the TRIAC dimmer 1250 can operate
properly.
[0171] As shown in FIG. 12, the bleeder unit 1220 includes a
bleeder-current generation sub-unit 12210 and a bleeder-current
control sub-unit 12220 according to certain embodiments. In some
embodiments, the bleeder-current generation sub-unit 12210 includes
an amplifier 1222, a transistor 1224, and a resistor 1226. In
certain embodiments, the bleeder-current control sub-unit 12220
includes amplifiers 1232.sub.1 and 1232.sub.2, switches 1234.sub.1
and 1234.sub.2, a resistor 1236, and a capacitor 1238.
[0172] In certain examples, if the control signal 1284.sub.1 is at
a logic low level, the positive input terminal (e.g., the "+"
terminal) of the amplifier 1222 is coupled to the output terminal
of the amplifier 1232.sub.1 through the switch 1234.sub.1, and if
the control signal 1284.sub.1 is at a logic high level, the
positive input terminal (e.g., the "+" terminal) of the amplifier
1222 is coupled to the output terminal of the amplifier 1232.sub.2
through the switch 1234.sub.1 and the resistor 1236. In some
examples, if the control signal 1284.sub.2 is at the logic high
level, the positive input terminal (e.g., the "+" terminal) of the
amplifier 1232.sub.2 is biased to the reference voltage 1288.sub.2
(e.g., V.sub.ref2) through the switch 1234.sub.2, and if the
control signal 1284.sub.2 is at the logic low level, the positive
input terminal (e.g., the "+" terminal) of the amplifier 1232.sub.2
is biased to the ground voltage (e.g., zero volts) through the
switch 1234.sub.2.
[0173] In some examples, if the transistor 1224 is in the
saturation region, the bleeder current 1290 is determined as
follows:
I bleed = V p R 2 ( Equation 12 ) ##EQU00012##
[0174] where I.sub.bleed represents the bleeder current 1290,
V.sub.p represents a voltage 1286 received by the amplifier 1222,
and R.sub.2 represents the resistance value of the resistor 1226.
In certain examples, the amplifier 1222 includes a positive input
terminal (e.g., the "+" terminal) and a negative input terminal
(e.g., the "-" terminal). For example, the voltage 1286 is received
by the positive input terminal of the amplifier 1222. As an
example, the voltage 1286 is controlled by the switch 1234.sub.1,
which makes the voltage 686 equal to either the output voltage of
the amplifier 1232.sub.2 or a reference voltage 1288.sub.1 (e.g.,
V.sub.ref1). For example, the reference voltage 1288.sub.1 is
received by the amplifier 1232.sub.1 (e.g., received by the
positive terminal of the amplifier 1232.sub.1) and is larger than
zero volts.
[0175] According to some embodiments, if the voltage 1276 indicates
that the phase range within which the TRIAC dimmer 1250 is in the
conduction state (e.g., on state) is smaller than the predetermined
conduction phase threshold and the voltage 1276 (e.g., V.sub.Is) is
smaller than the predetermined threshold voltage (e.g., V.sub.th1)
or if the voltage 1276 indicates that the phase range within which
the TRIAC dimmer 1250 is in the conduction state (e.g., on state)
is larger than the predetermined conduction phase threshold and the
sensing voltage 1282 (e.g., V.sub.sense) is smaller than the
predetermined threshold voltage (e.g., V.sub.th2), the control
signal 1284.sub.1 received by the bleeder unit 1220 sets the switch
1234.sub.1 so that the positive input terminal (e.g., the "+"
terminal) of the amplifier 1222 is biased to the reference voltage
1288.sub.1 through the amplifier 1232.sub.1 and the bleeder current
1290 is generated (e.g., the bleeder current 1290 being larger than
zero in magnitude).
[0176] According to certain embodiments, if the voltage 1276
indicates that the phase range within which the TRIAC dimmer 1250
is in the conduction state (e.g., on state) is smaller than the
predetermined conduction phase threshold and the voltage 1276
(e.g., V.sub.Is) is larger than the predetermined threshold voltage
(e.g., V.sub.th1) or if the voltage 1276 indicates that the phase
range within which the TRIAC dimmer 1250 is in the conduction state
(e.g., on state) is larger than the predetermined conduction phase
threshold and the sensing voltage 1282 (e.g., V.sub.sense) is
larger than the predetermined threshold voltage (e.g., V.sub.th2),
the control signal 1284.sub.1 received by the bleeder unit 1220
sets the switch 1234.sub.1 so that the positive input terminal
(e.g., the "+" terminal) of the amplifier 1222 is biased to the
output voltage of the amplifier 1232.sub.2 through the resistor
1236. As an example, the output voltage of the amplifier 1232.sub.2
is lower than the reference voltage 1288.sub.1 but still larger
than zero volts. For example, if the voltage 1286 is equal to the
output voltage of the amplifier 1232.sub.2, the bleeder current
1290 is generated (e.g., the bleeder current 1290 being larger than
zero in magnitude) but is smaller than the bleeder current 1290
generated when the voltage 1286 is equal to the reference voltage
1288.sub.1.
[0177] In some embodiments, if the voltage 1276 indicates that the
phase range within which the TRIAC dimmer 1250 is in the conduction
state (e.g., on state) is larger than or equal to the predetermined
conduction phase threshold and the sensing voltage 1282 (e.g.,
V.sub.sense) is smaller than the predetermined threshold voltage
(e.g., V.sub.th2), the control signal 1284.sub.1 received by the
bleeder unit 1220 sets the switch 1234.sub.1 so that the positive
input terminal (e.g., the "+" terminal) of the amplifier 1222 is
biased to the reference voltage 1288.sub.1 through the amplifier
1232.sub.1 and the bleeder current 1290 is generated (e.g., the
bleeder current 1290 being larger than zero in magnitude). In other
embodiment, if the voltage 1276 indicates that the phase range
within which the TRIAC dimmer 1250 is in the conduction state
(e.g., on state) is larger than or equal to the predetermined
conduction phase threshold and the sensing voltage 1282 (e.g.,
V.sub.sense) is larger than the predetermined threshold voltage
(e.g., V.sub.th2), the control signal 1284.sub.1 received by the
bleeder unit 1220 sets the switch 1234.sub.1 so that the positive
input terminal (e.g., the "+" terminal) of the amplifier 1222 is
biased to the output voltage of the amplifier 1232.sub.2 through
the resistor 1236.
[0178] In certain embodiments, the control signal 1284.sub.1,
through the switch 1234.sub.1, changes the voltage 1286 from being
equal to the reference voltage 1288.sub.1 (e.g., larger than zero
volts) to being equal to the output voltage of the amplifier
1232.sub.2 (e.g., lower than the reference voltage 1288.sub.1 but
still larger than zero volts) so that the bleeder current 1290
changes from being equal to a larger magnitude to being equal to a
smaller magnitude (e.g., a smaller magnitude that is larger than
zero). As shown in FIG. 12, the resistor 1236 and the capacitor
1238 are parts of an RC filtering circuit, which slows down the
decrease of the voltage 1286 from the reference voltage 1288.sub.1
to the output voltage of the amplifier 12322 (e.g., lower than the
reference voltage 1288.sub.1 but still larger than zero volts) and
also slows down the decrease of the bleeder current 1290 from being
equal to the larger magnitude to being equal to the smaller
magnitude (e.g., the smaller magnitude that is larger than zero)
according to some embodiments. For example, the bleeder unit 1220
is configured to reduce the bleeder current 1290 gradually (e.g.,
slowly) during a predetermined time duration, and the length of the
predetermined time duration depends on the resistance of the
resistor 1236 and the capacitance of the capacitor 1238.
[0179] In certain embodiments, the control signal 1284.sub.1,
through the switch 1234.sub.1, changes the voltage 1286 from being
equal to the output voltage of the amplifier 1232.sub.2 (e.g.,
lower than the reference voltage 1288.sub.1) to being equal to the
reference voltage 1288.sub.1 (e.g., larger than zero volts) so that
the bleeder current 1290 changes from being equal to the smaller
magnitude to being equal to the larger magnitude in order to for
the TRIAC dimmer 1250 to operate properly. In some examples, when
the voltage 1286 is biased to the reference voltage 1288.sub.1
(e.g., larger than zero volts), if the transistor 1224 is in the
saturation region, the bleeder current 1290 is determined as
follows:
I bleed = V ref 1 R 2 ( Equation 13 ) ##EQU00013##
[0180] where I.sub.bleed represents the bleeder current 1290,
V.sub.ref1 represents the reference voltage 1288.sub.1, and R.sub.2
represents the resistance value of the resistor 1226.
[0181] According to some embodiments, if the voltage 1276 indicates
that the phase range within which the TRIAC dimmer 1250 is in the
conduction state (e.g., on state) is smaller than the predetermined
conduction phase threshold and the voltage 1276 (e.g., V.sub.Is) is
smaller than the predetermined threshold voltage (e.g., V.sub.th1)
or if the voltage 1276 indicates that the phase range within which
the TRIAC dimmer 1250 is in the conduction state (e.g., on state)
is larger than the predetermined conduction phase threshold and the
sensing voltage 1282 (e.g., V.sub.sense) is smaller than the
predetermined threshold voltage (e.g., V.sub.th2), the control
signal 1284.sub.2 received by the bleeder unit 1220 sets the switch
1234.sub.2 so that the output terminal of the amplifier 1232.sub.2
is biased to a reference voltage 1288.sub.2 (e.g., V.sub.ref2)
through the amplifier 1232.sub.2. For example, the reference
voltage 1288.sub.2 is received by the amplifier 1232.sub.2 (e.g.,
received by the positive terminal of the amplifier 1232.sub.2) and
is larger than zero volts. As an example, the reference voltage
1288.sub.2 is smaller than the reference voltage 1288.sub.1. For
example, if the voltage 1286 is set to being equal to the output
voltage of the amplifier 1232.sub.2 and the output terminal of the
amplifier 1232.sub.2 is biased to the reference voltage 1288.sub.2
through the amplifier 1232.sub.2, the voltage 1286 is equal to the
reference voltage 1288.sub.2.
[0182] In some examples, when the voltage 1286 is biased to the
reference voltage 1288.sub.2 (e.g., larger than zero volts), if the
transistor 1224 is in the saturation region, the bleeder current
1290 is determined as follows:
I bleed = V ref 2 R 2 ( Equation 14 ) ##EQU00014##
[0183] where bleed represents the bleeder current 1290, V.sub.ref2
represents the reference voltage 1288.sub.2, and R.sub.2 represents
the resistance value of the resistor 1226.
[0184] According to certain embodiments, if the voltage 1276
indicates that the phase range within which the TRIAC dimmer 1250
is in the conduction state (e.g., on state) is smaller than the
predetermined conduction phase threshold and the voltage 1276
(e.g., V.sub.Is) is larger than the predetermined threshold voltage
(e.g., V.sub.th1) or if the voltage 1276 indicates that the phase
range within which the TRIAC dimmer 1250 is in the conduction state
(e.g., on state) is larger than the predetermined conduction phase
threshold and the sensing voltage 1282 (e.g., V.sub.sense) is
larger than the predetermined threshold voltage (e.g., V.sub.th2),
the control signal 1284.sub.2 received by the bleeder unit 1220
sets the switch 1234.sub.2 so that the output terminal of the
amplifier 1232.sub.2 is biased to the ground voltage (e.g., zero
volts). For example, if the voltage 1286 is set to being equal to
the output voltage of the amplifier 1232.sub.2 and the output
terminal of the amplifier 1232.sub.2 is biased to the ground
voltage (e.g., zero volts), the voltage 1286 is equal to the ground
voltage (e.g., zero volts).
[0185] In certain embodiments, the control signal 1284.sub.2,
through the switch 1234.sub.2, changes the output voltage of the
amplifier 1232.sub.2 from being equal to the reference voltage
1288.sub.2 to being equal to the ground voltage (e.g., zero volts).
As shown in FIG. 12, if the voltage 1286 is set to being equal to
the output voltage of the amplifier 1232.sub.2, the resistor 1236
and the capacitor 1238 are parts of the RC filtering circuit, which
slows down the decrease of the voltage 1286 from the reference
voltage 1288.sub.2 to the ground voltage (e.g., zero volts) and
also slows down the decrease of the bleeder current 1290 to zero
according to some embodiments. For example, the bleeder unit 1220
is configured to reduce the bleeder current 1290 gradually (e.g.,
slowly) during a predetermined time duration, and the length of the
predetermined time duration depends on the resistance of the
resistor 1236 and the capacitance of the capacitor 1238.
[0186] FIG. 13 is a simplified circuit diagram showing the bleeder
control unit 1230 of the LED lighting system 1200 as shown in FIG.
12 according to certain embodiments of the present invention. This
diagram is merely an example, which should not unduly limit the
scope of the claims. One of ordinary skill in the art would
recognize many variations, alternatives, and modifications. As
shown in FIG. 13, the bleeder control unit 1230 includes
comparators 1231.sub.0 and 1232.sub.0, delay sub-units 1235.sub.0
and 1236.sub.0, a conduction phase determination sub-unit
1238.sub.0 (e.g., a conduction phase detector), and a switch
1237.sub.0. Although the above has been shown using a selected
group of components for the bleeder control unit, there can be many
alternatives, modifications, and variations. For example, some of
the components may be expanded and/or combined. Other components
may be inserted to those noted above. Depending upon the
embodiment, the arrangement of components may be interchanged with
others replaced. Further details of these components are found
throughout the present specification.
[0187] In some embodiments, the comparator 1231.sub.0 includes
input terminals 1302 and 1304 and an output terminal 1306. As an
example, the input terminal 1302 receives the voltage 1276 (e.g.,
V.sub.Is), and the input terminal 1304 receives a threshold voltage
1390 (e.g., V.sub.th1). In certain examples, if the voltage 1276
(e.g., V.sub.Is) is larger than the threshold voltage 1390 (e.g.,
V.sub.th1), the TRIAC dimmer 1250 is in the conduction state (e.g.,
on state). In some examples, if the voltage 1276 (e.g., V.sub.Is)
is smaller than the threshold voltage 1390 (e.g., V.sub.th1), the
TRIAC dimmer 1250 is not in the conduction state (e.g., is in the
off state).
[0188] In certain embodiments, the comparator 1231.sub.0 compares
the voltage 1276 (e.g., V.sub.Is) and the threshold voltage 1390
(e.g., V.sub.th1) and generates a comparison signal 1396. For
example, if the voltage 1276 (e.g., V.sub.Is) is larger than the
threshold voltage 1390 (e.g., V.sub.th1), the comparator 1231.sub.0
generates the comparison signal 1396 at a logic high level. As an
example, if the voltage 1276 (e.g., V.sub.Is) is smaller than the
threshold voltage 1390 (e.g., V.sub.th1), the comparator 1231.sub.0
generates the comparison signal 1396 at a logic low level. In some
embodiments, if the voltage 1276 (e.g., V.sub.Is) changes from
being smaller than the threshold voltage 1390 (e.g., V.sub.th1) to
being larger than the threshold voltage 1390 (e.g., V.sub.th1), the
comparison signal 1396 changes from the logic low level to the
logic high level. As an example, the comparator 1231.sub.0 outputs
the comparison signal 1396 at the output terminal 1306.
[0189] According to some embodiments, the comparator 1232.sub.0
includes input terminals 1312 and 1314 and an output terminal 1316.
As an example, the input terminal 1312 receives the sensing voltage
1282 (e.g., V.sub.sense), and the input terminal 1314 receives a
threshold voltage 1392 (e.g., V.sub.th2). For example, the
threshold voltage 1392 (e.g., V.sub.th2) is smaller than the
reference voltage 1270 (e.g., V.sub.ref0) for the constant current
unit 1210. As an example, the threshold voltage 1392 (e.g.,
V.sub.th2) is equal to the threshold current (e.g., the holding
current of the TRIAC dimmer 1250) multiplied by the resistance
(e.g., R.sub.1) of the resistor 1262. In certain examples, if the
sensing voltage 1282 (e.g., V.sub.sense) is larger than the
threshold voltage 1392 (e.g., V.sub.th2), the LED current 1294 is
larger than the threshold current (e.g., the holding current of the
TRIAC dimmer 1250). In some examples, if the sensing voltage 1282
(e.g., V.sub.sense) is smaller than the threshold voltage 1392
(e.g., V.sub.th2), the LED current 1294 is smaller than the
threshold current (e.g., the holding current of the TRIAC dimmer
1250).
[0190] According to certain embodiments, the comparator 1232.sub.0
compares the sensing voltage 1282 (e.g., V.sub.sense) and the
threshold voltage 1392 (e.g., V.sub.th2) and generates a comparison
signal 1382. For example, if the sensing voltage 1282 (e.g.,
V.sub.sense) is larger than the threshold voltage 1392 (e.g.,
V.sub.th2), the comparator 1232.sub.0 generates the comparison
signal 1382 at a logic high level. As an example, if the sensing
voltage 1282 (e.g., V.sub.sense) is smaller than the threshold
voltage 1392 (e.g., V.sub.th2), the comparator 1232.sub.0 generates
the comparison signal 1382 at a logic low level. In some
embodiments, if the sensing voltage 1282 (e.g., V.sub.sense)
changes from being smaller than the threshold voltage 1392 (e.g.,
V.sub.th2) to being larger than the threshold voltage 1392 (e.g.,
V.sub.th2), the comparison signal 1382 changes from the logic low
level to the logic high level. As an example, the comparator
1232.sub.0 outputs the comparison signal 1382 at the output
terminal 1316.
[0191] As shown in FIG. 13, the conduction phase determination
sub-unit 1238.sub.0 is configured to receive the comparison signal
1396 from the comparator 1231.sub.0, compare a predetermined
conduction phase threshold and the phase range within which the
TRIAC dimmer 1250 is in the conduction state (e.g., on state) or
compare a predetermined non-conduction phase threshold and the
phase range within which the TRIAC dimmer 1250 is not in the
conduction state (e.g., is in the off state), and generate a
detection signal 1380 based at least in part on the comparison,
according to some embodiments. For example, the detection signal
1380 is received by the switch 1237.sub.0, which controls whether
the comparison signal 1396 or the comparison signal 1382 is
received by the delay sub-unit 1235.sub.0 as a signal 1384. In
certain examples, if the phase range within which the TRIAC dimmer
1250 is in the conduction state (e.g., on state) is smaller than
the predetermined conduction phase threshold, the comparison signal
1396 is received by the delay sub-unit 1235.sub.0 as the signal
1384. In some examples, if the phase range within which the TRIAC
dimmer 1250 is in the conduction state (e.g., on state) is larger
than the predetermined conduction phase threshold, the comparison
signal 1382 is received by the delay sub-unit 1235.sub.0 as the
signal 1384.
[0192] In certain embodiments, the conduction phase determination
sub-unit 1238.sub.0 includes a duration determination component
1233.sub.0 (e.g., a duration determination device) and a phase
detection component 1234.sub.0 (e.g., a phase detection device). In
some examples, the duration determination component 1233.sub.0 is
configured to receive a clock signal 1394 (e.g., CLK) and the
comparison signal 1396, and determine, within each cycle of the
rectified voltage 1298 (e.g., VIN), the time duration during which
the comparison signal 1396 indicates that the voltage 1276 (e.g.,
V.sub.Is) is smaller than the threshold voltage 1390 (e.g.,
V.sub.th1) (e.g., during which the TRIAC dimmer 1250 is not in the
conduction state), and the duration determination component
1233.sub.0 is further configured to generates a signal 1398
representing the determined time duration. For example, the signal
1398 is received by the phase detection component 1234.sub.0.
[0193] In certain examples, the phase detection component
1234.sub.0 is configured to receive the signal 1398 representing
the determined time duration, determine whether the determined
duration is larger than a predetermined duration threshold, and
generates the detection signal 1380 based on at least the
determined duration and the predetermined duration threshold. For
example, the detection signal 1380 is received by the switch
1237.sub.0. As an example, if the detection signal 1380 indicates
that the determined duration is larger than the predetermined
duration threshold, the switch 1237.sub.0 sets the comparison
signal 1396 to be the signal 1384 that is received by the delay
sub-unit 1235.sub.0. For example, if the detection signal 1380
indicates that the determined duration is smaller than the
predetermined duration threshold, the switch 1237.sub.0 sets the
comparison signal 1382 to be the signal 1384 that is received by
the delay sub-unit 1235.sub.0.
[0194] According to certain embodiments, within each cycle of the
rectified voltage 1298 (e.g., VIN), the time duration during which
the voltage 1276 (e.g., V.sub.Is) is smaller than the threshold
voltage 1390 (e.g., V.sub.th1) corresponds to the phase range
within which the TRIAC dimmer 1250 is not in the conduction state
(e.g., is in the off state). According to some embodiments, within
each cycle of the rectified voltage 1298 (e.g., VIN), the time
duration during which the voltage 1276 (e.g., V.sub.Is) is larger
than the threshold voltage 1390 (e.g., V.sub.th1) corresponds to
the phase range within which the TRIAC dimmer 1250 is in the
conduction state (e.g., on state).
[0195] In some embodiments, the phase range within which the TRIAC
dimmer 1250 is in the conduction state (e.g., on state) being
smaller than the predetermined conduction phase threshold
corresponds to the phase range within which the TRIAC dimmer 1250
is not in the conduction state (e.g., is in the off state) being
larger than the predetermined non-conduction phase threshold. In
certain embodiments, the phase range within which the TRIAC dimmer
1250 is in the conduction state (e.g., on state) being larger than
the predetermined conduction phase threshold corresponds to the
phase range within which the TRIAC dimmer 950 is not in the
conduction state (e.g., is in the off state) being smaller than the
predetermined non-conduction phase threshold.
[0196] According to certain embodiments, the signal 1384 is
received by the delay sub-unit 12350, which in response generates
the control signal 12841. For example, if the signal 1384 changes
from the logic low level to the logic high level, the delay
sub-unit 12350, after a predetermined delay (e.g., after t.sub.d1),
changes the control signal 1284.sub.1 from the logic low level to
the logic high level. As an example, if the signal 1384 changes
from the logic high level to the logic low level, the delay
sub-unit 12350, without any predetermined delay (e.g., without
t.sub.d1), changes the control signal 1284.sub.1 from the logic
high level to the logic low level.
[0197] According to certain embodiments, the control signal
1284.sub.1 is received by the delay sub-unit 1236.sub.0, which in
response generates the control signal 1284.sub.2. For example, if
the control signal 1284.sub.1 changes from the logic low level to
the logic high level, the delay sub-unit 1236.sub.0, after a
predetermined delay (e.g., after t.sub.d2), changes the control
signal 1284.sub.2 from the logic high level to the logic low level.
As an example, if the control signal 1284.sub.1 changes from the
logic high level to the logic low level, the delay sub-unit
1236.sub.0, without any predetermined delay (e.g., without
t.sub.d2), changes the control signal 1284.sub.2 from the logic low
level to the logic high level.
[0198] According to some embodiments, if the signal 1384 changes
from the logic low level to the logic high level, the control
signal 1284.sub.1, after a predetermined delay (e.g., after
t.sub.d1), changes from the logic low level to the logic high
level, and the control signal 12842, after two predetermined delays
(e.g., after both t.sub.d1 and t.sub.d2), changes from the logic
high level to the logic low level. According to certain
embodiments, if the signal 1384 changes from the logic high level
to the logic low level, the control signal 1284.sub.1, without any
predetermined delay, changes from the logic high level to the logic
low level, and the control signal 1284.sub.2, without any
predetermined delay, changes from the logic low level to the logic
high level.
[0199] As shown in FIG. 12, if the control signal 1284.sub.1 is at
the logic high level, the switch 1234.sub.1 is set to bias the
voltage 1286 to the output voltage of the amplifier 1232.sub.2, and
if the control signal 1284.sub.1 is at the logic low level, the
switch 1234.sub.1 is set to bias the voltage 1286 to the reference
voltage 1288.sub.1 (e.g., being larger than zero volts), according
to some embodiments. For example, if the control signal 1284.sub.1
changes from the logic high level to the logic low level, the
voltage 1286 changes from the output voltage of the amplifier
1232.sub.2 to the reference voltage 1288.sub.1 (e.g., being larger
than zero volts). As an example, if the control signal 1284.sub.1
changes from the logic low level to the logic high level, the
voltage 1286 changes from the reference voltage 1288.sub.1 (e.g.,
being larger than zero volts) to the output voltage of the
amplifier 1232.sub.2.
[0200] In certain embodiments, if the voltage 1276 indicates that
the phase range within which the TRIAC dimmer 1250 is in the
conduction state (e.g., on state) is smaller than the predetermined
conduction phase threshold and the voltage 1276 (e.g., V.sub.Is)
changes from being smaller than the predetermined threshold voltage
(e.g., Vflit) to being larger than the predetermined threshold
voltage (e.g., V.sub.th1) or if the voltage 1276 indicates that the
phase range within which the TRIAC dimmer 1250 is in the conduction
state (e.g., on state) is larger than the predetermined conduction
phase threshold and the sensing voltage 1282 (e.g., V.sub.sense)
changes from being smaller than the predetermined threshold voltage
(e.g., V.sub.th2) to being larger than the predetermined threshold
voltage (e.g., V.sub.th2), the bleeder current 1290, after one
predetermined delay (e.g., after t.sub.d1) from the time of change,
changes from the larger magnitude to the smaller magnitude (e.g.,
the smaller magnitude that is larger than zero) during the
predetermined time duration, and after two predetermined delays
(e.g., after t.sub.d1 and t.sub.d2) from the time of change,
further changes from the smaller magnitude (e.g., the smaller
magnitude that is larger than zero) to zero during the
predetermined time duration. For example, the predetermined delay
t.sub.d1 is provided by the delay sub-unit 12350, and the
predetermined delay tae is provided by the delay sub-unit 12360. As
an example, the falling edge of the control signal 1284.sub.2 is
delayed from the rising edge of the control signal 1284.sub.1 by
the predetermined delay t.sub.d2. For example, the length of the
predetermined time duration depends on the resistance of the
resistor 1236 and the capacitance of the capacitor 1238.
[0201] In some embodiments, if the voltage 1276 indicates that the
phase range within which the TRIAC dimmer 1250 is in the conduction
state (e.g., on state) is smaller than the predetermined conduction
phase threshold and the voltage 1276 (e.g., V.sub.Is) changes from
being larger than the predetermined threshold voltage (e.g.,
V.sub.th1) to being smaller than the predetermined threshold
voltage (e.g., V.sub.th1) or if the voltage 1276 indicates that the
phase range within which the TRIAC dimmer 1250 is in the conduction
state (e.g., on state) is larger than the predetermined conduction
phase threshold and the sensing voltage 1282 (e.g., V.sub.sense)
changes from being larger than the predetermined threshold voltage
(e.g., V.sub.th2) to being smaller than the predetermined threshold
voltage (e.g., V.sub.th2), the bleeder current 1290, without any
predetermined delay (e.g., without to and without t.sub.d2),
changes to a magnitude according to Equation 13.
[0202] As shown in FIG. 12 and FIG. 13, two levels of control
mechanisms are used by the bleeder-current control sub-unit 12220
so that gradual (e.g., slow) reduction of the bleeder current 1290
is accomplished in two corresponding stages according to certain
embodiments. In some examples, the amplifier 1232.sub.1 and the
switch 1234.sub.1, together with the resistor 1236 and the
capacitor 1238, are used to implement the first level of control
mechanism for the first stage, and the amplifier 1232.sub.2 and the
switch 1234.sub.2, together with the resistor 1236 and the
capacitor 1238, are used to implement the second level of control
mechanism for the second stage. In certain example, the switch
1234.sub.1 is controlled by the control signal 1284.sub.1 and the
switch 1234.sub.2 is controlled by the control signal 1284.sub.2,
so that the bleeder current 1290 becomes zero in two stages. For
example, in the first stage, the voltage 1286 decreases from the
reference voltage 1288.sub.1 (e.g., V.sub.ref1) to the reference
voltage 1288.sub.2 (e.g., V.sub.ref2) and the bleeder current 1290
decreases from the current level as determined by Equation 13 to
the current level as determined by Equation 14. As an example, in
the second stage, the voltage 1286 further decreases from the
reference voltage 1288.sub.2 (e.g., V.sub.ref2) to the ground
voltage (e.g., zero volts) and the bleeder current 1290 further
decreases from the current level as determined by Equation 14 to
zero.
[0203] According to certain embodiments, the LED lighting system
1200 as shown in FIGS. 12 and 13 provides one or more advantages.
For example, if the phase range within which the TRIAC dimmer 1250
is in the conduction state (e.g., on state) is so small that the
TRIAC dimmer 1250 is in the conduction state (e.g., on state) only
when the rectified voltage 1298 (e.g., VIN) is small and the
sensing voltage 1282 (e.g., V.sub.sense) is smaller than the
threshold voltage 1392 (e.g., V.sub.th2), the LED lighting system
1200 does not allow the bleeder current 1290 to be generated when
the voltage 1276 (e.g., V.sub.Is) is larger than the threshold
voltage 1390 (e.g., Vthl). As an example, if the phase range within
which the TRIAC dimmer 1250 is in the conduction state (e.g., on
state) is smaller than the predetermined conduction phase
threshold, the LED lighting system 1200 allows or does not allow
the bleeder current 1290 to be generated based on the comparison
between the voltage 1276 (e.g., V.sub.Is) and the threshold voltage
1390 (e.g., V.sub.th1), in order to stabilize the conduction state
(e.g., on state) of the TRIAC dimmer 1250, stabilize the LED
current 1294 (e.g., I.sub.LED), and/or reduce (e.g., eliminate)
blinking of the one or more LEDs 1242.
[0204] As discussed above and further emphasized here, FIG. 12 and
FIG. 13 are merely examples, which should not unduly limit the
scope of the claims. One of ordinary skill in the art would
recognize many variations, alternatives, and modifications. In some
embodiments, N levels of control mechanisms are used by the
bleeder-current control sub-unit 12220 so that gradual (e.g., slow)
reduction of the bleeder current 1290 is accomplished in N
corresponding stages, where N is an integer larger than 1. For
example, N is larger than 2. In certain examples, the change of a
control signal 1284.sub.n occurs after a delay of tan from the time
when the change of a control signal 1284.sub.n-1 occurs, where n is
an integer larger than 1 but smaller than or equal to N. As an
example, the change of the control signal 1284.sub.2 occurs after
the delay of t.sub.d2 from the time when the change of the control
signal 1284.sub.1 occurs. For example, the change of the control
signal 1284.sub.3 occurs after a delay of to from the time when the
change of the control signal 1284.sub.2 occurs. As an example, the
change of the control signal 684N occurs after a delay of t.sub.dN
from the time when the change of the control signal 684.sub.N-1
occurs.
[0205] In certain embodiments, the bleeder-current control sub-unit
12220 includes amplifiers 1232.sub.1, . . . , 1232.sub.k, . . . ,
and 1232.sub.N, switches 1234.sub.1, . . . , 1234.sub.k, . . . ,
and 1234.sub.N, the resistor 1236, and the capacitor 1238, where k
is an integer larger than 1 but smaller than N. For example, a
negative input terminal of the amplifier 1232.sub.k is coupled to
an output terminal of the amplifier 632.sub.k. As an example, the
capacitor 1238 is biased between the voltage 1286 (e.g., V.sub.p)
and the ground voltage. In some examples, the positive input
terminal of the amplifier 1232.sub.1 is biased to the reference
voltage 1288.sub.1 (e.g., V.sub.ref1). For example, the switch
1234.sub.1 is controlled by the control signal 1284.sub.1 (e.g.,
Ctr.sub.1) so that the voltage 1286 (e.g., V.sub.p) either equals
the reference voltage 1288.sub.1 (e.g., V.sub.ref1) to generate the
bleeder current 1290 (e.g., I.sub.bleed) based at least in part on
the reference voltage 1288.sub.1 (e.g., V.sub.ref1), or equals the
output voltage of the amplifier 1232.sub.2 (e.g., through the
resistor 1236) to generate the bleeder current 1290 (e.g.,
I.sub.bleed) based at least in part on the output voltage of the
amplifier 1232.sub.2. As an example, the switch 1234.sub.2 is
controlled by the control signal 1284.sub.2 (e.g., Ctr.sub.2) so
that the voltage 1286 (e.g., V.sub.p) either equals the reference
voltage 1288.sub.2 (e.g., V.sub.ref2) to generate the bleeder
current 1290 (e.g., I.sub.bleed) based at least in part on the
reference voltage 1288.sub.2 (e.g., V.sub.ref2), or equals the
output voltage of the amplifier 1232.sub.3 to generate the bleeder
current 1290 (e.g., I.sub.bleed) based at least in part on the
output voltage of the amplifier 1232.sub.3. For example, the switch
1234k is controlled by the control signal 1284k (e.g., Ctr.sub.k)
so that the voltage 1286 (e.g., V.sub.p) either equals the
reference voltage 1288k (e.g., V.sub.refk) to generate the bleeder
current 1290 (e.g., I.sub.bleed) based at least in part on the
reference voltage 1288k (e.g., V.sub.refk), or equals the output
voltage of the amplifier 1232.sub.k+1 to generate the bleeder
current 1290 (e.g., I.sub.bleed) based at least in part on the
output voltage of the amplifier 1232.sub.k+1. As an example, the
switch 1234.sub.N is controlled by the control signal 1284.sub.N
(e.g., Ctr.sub.N) so that the voltage 1286 (e.g., V.sub.p) either
equals the reference voltage 1288.sub.N (e.g., V.sub.refN) to
generate the bleeder current 1290 (e.g., I.sub.bleed) based at
least in part on the reference voltage 1288.sub.N (e.g.,
V.sub.refN), or equals the ground voltage (e.g., zero volts) to
reduce the bleeder current 1290 (e.g., I.sub.bleed) to zero. In
certain examples, the reference voltage 1288.sub.j (e.g.,
V.sub.refj) is larger than zero volts but smaller than the
reference voltage 688.sub.j+1 (e.g., V.sub.ref(j+1)), where j is an
integer larger than 0 but smaller than N.
[0206] In some embodiments, the bleeder control unit 1230 includes
comparators 1231.sub.0 and 1232.sub.0, delay sub-units 12350.sub.1,
. . . 12350.sub.m, . . . and 12350.sub.N, the conduction phase
determination sub-unit 12380, and the switch 12370, where N is an
integer larger than 1 and m is an integer larger than 1 but smaller
than N. For example, the delay sub-unit 12350.sub.1 is the delay
sub-unit 12350 as shown in FIG. 13. As an example, the delay
sub-unit 12350.sub.2 is the delay sub-unit 12360 as shown in FIG.
13.
[0207] In certain examples, the change of the control signal
1284.sub.1 occurs after a delay of to from the time when the change
of the signal 1384 occurs, either in response to the phase range
within which the TRIAC dimmer 1250 is in the conduction state
(e.g., on state) being smaller than the predetermined conduction
phase threshold and the voltage 1276 (e.g., V.sub.Is) changing from
being smaller than the predetermined threshold voltage (e.g.,
V.sub.th1) to being larger than the predetermined threshold voltage
(e.g., V.sub.th1), or in response to the phase range within which
the TRIAC dimmer 1250 is in the conduction state (e.g., on state)
being larger than the predetermined conduction phase threshold and
the sensing voltage 1282 (e.g., V.sub.sense) changing from being
smaller than the predetermined threshold voltage (e.g., V.sub.th2)
to being larger than the predetermined threshold voltage (e.g.,
V.sub.th2).
[0208] In some examples, the change of the control signal
1284.sub.m occurs after a delay of tam from the time when the
change of the control signal 1284.sub.m-1 occurs, either in
response to the phase range within which the TRIAC dimmer 1250 is
in the conduction state (e.g., on state) being smaller than the
predetermined conduction phase threshold and the voltage 1276
(e.g., V.sub.Is) changing from being smaller than the predetermined
threshold voltage (e.g., V.sub.th1) to being larger than the
predetermined threshold voltage (e.g., V.sub.th1), or in response
to the phase range within which the TRIAC dimmer 1250 is in the
conduction state (e.g., on state) being larger than the
predetermined conduction phase threshold and the sensing voltage
1282 (e.g., V.sub.sense) changing from being smaller than the
predetermined threshold voltage (e.g., V.sub.th2) to being larger
than the predetermined threshold voltage (e.g., V.sub.th2).
[0209] In certain examples, the change of the control signal
1284.sub.N occurs after a delay of t.sub.dN from the time when the
change of the control signal 1284.sub.N-1 occurs, either in
response to the phase range within which the TRIAC dimmer 1250 is
in the conduction state (e.g., on state) being smaller than the
predetermined conduction phase threshold and the voltage 1276
(e.g., V.sub.Is) changing from being smaller than the predetermined
threshold voltage (e.g., V.sub.th1) to being larger than the
predetermined threshold voltage (e.g., V.sub.th1), or in response
to the phase range within which the TRIAC dimmer 1250 is in the
conduction state (e.g., on state) being larger than the
predetermined conduction phase threshold and the sensing voltage
1282 (e.g., V.sub.sense) changing from being smaller than the
predetermined threshold voltage (e.g., V.sub.th2) to being larger
than the predetermined threshold voltage (e.g., V.sub.th2).
[0210] In some embodiments, the bleeder control unit 1230 outputs
the control signal 1284.sub.1, . . . the control signal 1284.sub.m,
. . . and the control signal 1284N to the bleeder-current control
sub-unit 12220. For example, the control signal 1284.sub.1, . . .
the control signal 1284.sub.m, . . . and the control signal
1284.sub.N are used to control the switch 1234.sub.1, . . . the
switch 1234.sub.m, . . . and the switch 1234.sub.N.
[0211] FIG. 14 is a simplified diagram showing a method for the LED
lighting system 900 as shown in FIG. 9 according to some
embodiments of the present invention. This diagram is merely an
example, which should not unduly limit the scope of the claims. One
of ordinary skill in the art would recognize many variations,
alternatives, and modifications. As shown in FIG. 14, the method
1400 includes a process 1410 for determining whether the phase
range within which the TRIAC dimmer is in the conduction state is
larger than or equal to the predetermined conduction phase
threshold, a process 1420 for generating the control signal to
allow or not allow the bleeder unit to generate the bleeder current
depending on the comparison between a predetermined threshold
voltage and the sensing voltage proportional to the LED current, a
process 1430 for generating the control signal to allow or not
allow the bleeder unit to generate the bleeder current depending on
the comparison between a predetermined threshold voltage and the
voltage proportional to the rectified voltage, and a process 1440
for allowing or not allowing the bleeder current to be generated in
response to the control signal. For example, the method 1400 is
implemented by at least the LED lighting system 900. Although the
above has been shown using a selected group of processes for the
method, there can be many alternatives, modifications, and
variations. For example, some of the processes may be expanded
and/or combined. Other processes may be inserted to those noted
above. Depending upon the embodiment, the arrangement of processes
may be interchanged with others replaced. Further details of these
processes are found throughout the present specification.
[0212] At the process 1410, whether the phase range within which
the TRIAC dimmer is in the conduction state (e.g., on state) is
larger than or equal to the predetermined conduction phase
threshold is determined according to certain embodiments. In some
examples, the bleeder control unit 930 uses the voltage 976 (e.g.,
V.sub.Is) to determine whether the voltage 976 (e.g., V.sub.Is)
indicates that the phase range within which the TRIAC dimmer 950 is
in the conduction state (e.g., on state) is larger than or equal to
the predetermined conduction phase threshold. As an example, the
voltage 976 (e.g., V.sub.Is) is proportional to the rectified
voltage 998 (e.g., VIN) according to Equation 7. For example, if
the phase range within which the TRIAC dimmer is in the conduction
state (e.g., on state) is determined to be larger than or equal to
the predetermined conduction phase threshold, the process 1420 is
performed. As an example, if the phase range within which the TRIAC
dimmer is in the conduction state (e.g., on state) is determined
not to be larger than or equal to the predetermined conduction
phase threshold, the process 1430 is performed.
[0213] At the process 1420, the control signal is generated to
allow or not allow the bleeder unit to generate the bleeder current
depending on the comparison between a predetermined threshold
voltage and the sensing voltage that is proportional to the LED
current according to some embodiments. In certain examples, the
bleeder control unit 930 uses the comparison between the sensing
voltage 982 (e.g., V.sub.sense) and the predetermined threshold
voltage 1092 (e.g., V.sub.th2) to generate the control signal 984
in order to allow or not allow the bleeder unit 920 to generate the
bleeder current 990. For example, the sensing voltage 982 (e.g.,
V.sub.sense) is proportional to the LED current 994 (e.g.,
I.sub.LED) (e.g., the sensing voltage 982 being equal to the LED
current 994 multiplied by the resistance of the resistor 962).
[0214] At the process 1430, the control signal is generated to
allow or not allow the bleeder unit to generate the bleeder current
depending on the comparison between a predetermined threshold
voltage and the voltage that is proportional to the rectified
voltage according to certain embodiments. In some examples, the
bleeder control unit 930 uses the comparison between the voltage
976 (e.g., V.sub.Is) and the predetermined threshold voltage 1090
(e.g., V.sub.th1) to generate the control signal 984 in order to
allow or not allow the bleeder unit 920 to generate the bleeder
current 990. For example, the voltage 976 (e.g., V.sub.Is) is
proportional to the rectified voltage 998 (e.g., VIN) according to
Equation 7.
[0215] At the process 1440, the bleeder current is allowed or not
allowed to be generated in response to the control signal according
to certain embodiments according to some embodiments. In certain
examples, the bleeder unit 920 receives the control signal 984
(e.g., the control signal 984 that is generated by the process 1420
or the process 1430) and in response allows or does not allow the
bleeder current 990 to be generated. For example, after the
predetermined delay (e.g., after t.sub.d) provided by the delay
sub-unit 9350, the bleeder current 990 changes from being equal to
the high current level (e.g., being larger than zero) to being
equal to zero gradually (e.g., slowly) during the predetermined
time duration as shown by the waveform 1190 in FIG. 11. As an
example, the length of the predetermined time duration depends on
the resistance of the resistor 936 and the capacitance of the
capacitor 938.
[0216] As discussed above and further emphasized here, FIG. 14 is
merely an example, which should not unduly limit the scope of the
claims. One of ordinary skill in the art would recognize many
variations, alternatives, and modifications. In some examples, at
the process 1410, whether the phase range within which the TRIAC
dimmer is in the conduction state (e.g., on state) is larger than
or smaller than the predetermined conduction phase threshold is
determined. For example, if the phase range within which the TRIAC
dimmer is in the conduction state (e.g., on state) is determined to
be larger than the predetermined conduction phase threshold, the
process 1420 is performed. As an example, if the phase range within
which the TRIAC dimmer is in the conduction state (e.g., on state)
is determined to be smaller than the predetermined conduction phase
threshold, the process 1430 is performed.
[0217] FIG. 15 is a simplified diagram showing a method for the LED
lighting system 1200 as shown in FIG. 12 according to certain
embodiments of the present invention. This diagram is merely an
example, which should not unduly limit the scope of the claims. One
of ordinary skill in the art would recognize many variations,
alternatives, and modifications. As shown in FIG. 15, the method
1500 includes a process 1510 for determining whether the phase
range within which the TRIAC dimmer is in the conduction state is
larger than or equal to the predetermined conduction phase
threshold, a process 1520 for generating the signal based on at
least the comparison between a predetermined threshold voltage and
the sensing voltage proportional to the LED current, a process 1530
for generating the signal based on at least the comparison between
a predetermined threshold voltage and the voltage proportional to
the rectified voltage, a process 1540 for generating multiple
control signals with multiple corresponding delays to not allow the
bleeder current to be generated, and a process 1550 for not
allowing the bleeder current to be generated in response to the
multiple control signals so that the bleeder current gradually
decreases in multiple stages respectively. For example, the method
1500 is implemented by at least the LED lighting system 1200.
Although the above has been shown using a selected group of
processes for the method, there can be many alternatives,
modifications, and variations. For example, some of the processes
may be expanded and/or combined. Other processes may be inserted to
those noted above. Depending upon the embodiment, the arrangement
of processes may be interchanged with others replaced. Further
details of these processes are found throughout the present
specification.
[0218] At the process 1510, whether the phase range within which
the TRIAC dimmer is in the conduction state (e.g., on state) is
larger than or equal to the predetermined conduction phase
threshold is determined according to certain embodiments. In some
examples, the bleeder control unit 1230 uses the voltage 1276
(e.g., V.sub.Is) to determine whether the voltage 1276 (e.g.,
V.sub.Is) indicates that the phase range within which the TRIAC
dimmer 1250 is in the conduction state (e.g., on state) is larger
than or equal to the predetermined conduction phase threshold. As
an example, the voltage 1276 (e.g., V.sub.Is) is proportional to
the rectified voltage 1298 (e.g., VIN) according to Equation 11.
For example, if the phase range within which the TRIAC dimmer is in
the conduction state (e.g., on state) is determined to be larger
than or equal to the predetermined conduction phase threshold, the
process 1520 is performed. As an example, if the phase range within
which the TRIAC dimmer is in the conduction state (e.g., on state)
is determined not to be larger than or equal to the predetermined
conduction phase threshold, the process 1530 is performed.
[0219] At the process 1520, the signal is generated based on at
least the comparison between a predetermined threshold voltage and
the sensing voltage that is proportional to the LED current
according to some embodiments. In certain examples, the bleeder
control unit 1230 uses the comparison between the sensing voltage
1282 (e.g., V.sub.sense) and the predetermined threshold voltage
1392 (e.g., V.sub.th2) to generate the signal 1384. For example,
the sensing voltage 1282 (e.g., V.sub.sense) is proportional to the
LED current 1294 (e.g., I.sub.LED) (e.g., the sensing voltage 1282
being equal to the LED current 1294 multiplied by the resistance of
the resistor 1262).
[0220] At the process 1530, the signal is generated based on at
least the comparison between a predetermined threshold voltage and
the voltage that is proportional to the rectified voltage according
to certain embodiments. In some examples, the bleeder control unit
1230 uses the comparison between the voltage 1276 (e.g., V.sub.Is)
and the predetermined threshold voltage 1304 (e.g., V.sub.th1) to
generate the signal 1384. For example, the voltage 1276 (e.g.,
V.sub.Is) is proportional to the rectified voltage 1298 (e.g., VIN)
according to Equation 11.
[0221] At the process 1540, multiple control signals are generated
with multiple corresponding delays to not allow the bleeder current
to be generated if one or more predetermined conditions are
satisfied according some embodiments. In certain examples, the
multiple control signals include the control signals 1284.sub.1, ,
1284.sub.n, . . . , and 1284.sub.N, where N is an integer larger
than 1 and n is an integer larger than 1 but smaller than or equal
to N. In some examples, if the voltage 1276 indicates that the
phase range within which the TRIAC dimmer 1250 is in the conduction
state (e.g., on state) is smaller than the predetermined conduction
phase threshold and the voltage 1276 (e.g., V.sub.Is) changes from
being smaller than the predetermined threshold voltage (e.g.,
V.sub.th1) to being larger than the predetermined threshold voltage
(e.g., V.sub.th1) or if the voltage 1276 indicates that the phase
range within which the TRIAC dimmer 1250 is in the conduction state
(e.g., on state) is larger than the predetermined conduction phase
threshold and the sensing voltage 1282 (e.g., V.sub.sense) changes
from being smaller than the predetermined threshold voltage (e.g.,
V.sub.th2) to being larger than the predetermined threshold voltage
(e.g., V.sub.th2), the change of the control signal 1284.sub.n
occurs after a delay of tan from the time when the change of the
control signal 1284.sub.n-1 occurs, where n is an integer larger
than 1 but smaller than or equal to N. As an example, the change of
the control signal 1284.sub.2 occurs after the delay of t.sub.d2
from the time when the change of the control signal 1284.sub.1
occurs. For example, the change of the control signal 1284.sub.3
occurs after a delay of to from the time when the change of the
control signal 1284.sub.2 occurs. As an example, the change of the
control signal 684.sub.N occurs after a delay of taN from the time
when the change of the control signal 684.sub.N-1 occurs.
[0222] At the process 1550, the bleeder current is not allowed to
be generated in response to the multiple control signals so that
the bleeder current gradually (e.g., slowly) decreases in multiple
stages respectively. In certain examples, the bleeder unit 1220
receives the multiple control signals that is generated by the
process 1540 (e.g., the control signals 1284.sub.1, . . . ,
1284.sub.n, . . . , and 1284.sub.N, where N is an integer larger
than 1 and n is an integer larger than 1 but smaller than or equal
to N), and in response does not allow the bleeder current 1290 to
be generated. In some examples, the bleeder current 1290 decreases
gradually (e.g., slowly) during the predetermined time duration. As
an example, for the j.sup.th stage of the multiple stages, the
bleeder current 1290 decreases gradually (e.g., slowly) during the
predetermined time duration from the reference voltage 1288.sub.j
(e.g., V.sub.refj) divided by the resistance value (e.g., R.sub.2)
of the resistor 1226 to the reference voltage 1288.sub.j+1 (e.g.,
V.sub.ref(j+1)) divided by the resistance value (e.g., R.sub.2) of
the resistor 1226, where j is an integer larger than zero but
smaller than N. For example, for the N.sup.th stage of the multiple
stages, the bleeder current 1290 decreases gradually (e.g., slowly)
during the predetermined time duration from the reference voltage
1288.sub.N (e.g., V.sub.refN) divided by the resistance value
(e.g., R.sub.2) of the resistor 1226 to zero, where N is an integer
larger than 1. In some examples, the length of the predetermined
time duration depends on the resistance of the resistor 1236 and
the capacitance of the capacitor 1238.
[0223] As discussed above and further emphasized here, FIG. 15 is
merely an example, which should not unduly limit the scope of the
claims. One of ordinary skill in the art would recognize many
variations, alternatives, and modifications. In certain examples,
at the process 1510, whether the phase range within which the TRIAC
dimmer is in the conduction state (e.g., on state) is larger than
or smaller than the predetermined conduction phase threshold is
determined. For example, if the phase range within which the TRIAC
dimmer is in the conduction state (e.g., on state) is determined to
be larger than the predetermined conduction phase threshold, the
process 1520 is performed. As an example, if the phase range within
which the TRIAC dimmer is in the conduction state (e.g., on state)
is determined to be smaller than the predetermined conduction phase
threshold, the process 1530 is performed.
[0224] According to certain embodiments, the present invention
provides one or more systems and/or one or more methods for
controlling one or more light emitting diodes. In some examples, an
RC filtering circuit is used to control the reduction of a bleeder
current so that the bleeder current gradually decreases during a
predetermined time duration. As an example, a predetermined delay
is used to delay the starting time of the gradual reduction of the
bleeder current in order to stabilize the conduction state (e.g.,
on state) of a TRIAC dimmer. For example, two or more levels of
control mechanisms are used so that the gradual reduction of the
bleeder current is accomplished in two or more stages respectively
to further reduce (e.g., eliminate) the oscillation of a rectified
voltage and further reduce (e.g., eliminate) blinking of the one or
more LEDs. In certain examples, a phase range within which the
TRIAC dimmer is in the conduction state (e.g., on state) is
detected and used to either select a sensing voltage proportional
to an LED current or select a voltage proportional to the rectified
voltage for controlling the bleeder current, in order to stabilize
the conduction state (e.g., on state) of the TRIAC dimmer,
stabilize the LED current, and/or reduce (e.g., eliminate) blinking
of the one or more LEDs. For example, such use of the phase range
within which the TRIAC dimmer is in the conduction state (e.g., on
state) can, when the phase range is small, prevent the bleeder
current from always being allowed to be generated and also prevent
the bleeder current changes back and forth between being allowed to
be generated and not being allowed to be generated. As an example,
such use of the phase range within which the TRIAC dimmer is in the
conduction state (e.g., on state) can stabilize the conduction
state (e.g., on state) of the TRIAC dimmer.
[0225] According to some embodiments, a system for controlling one
or more light emitting diodes includes: a current regulator
including a first regulator terminal and a second regulator
terminal, the first regulator terminal being configured to receive
a diode current flowing through the one or more light emitting
diodes, the current regulator being configured to generate a
sensing signal representing the diode current, the second regulator
terminal being configured to output the sensing signal; a bleeder
controller including a first controller terminal and a second
controller terminal, the first controller terminal being configured
to receive the sensing signal from the second regulator terminal,
the bleeder controller being configured to generate a first bleeder
control signal based at least in part on the sensing signal, the
second controller terminal being configured to output the first
bleeder control signal, the first bleeder control signal indicating
whether a bleeder current is allowed or not allowed to be
generated; and a bleeder including a first bleeder terminal and a
second bleeder terminal, the first bleeder terminal being
configured to receive the first bleeder control signal from the
second controller terminal, the second bleeder terminal being
configured to receive a rectified voltage associated with a TRIAC
dimmer and generated by a rectifying bridge; wherein: the bleeder
includes a current controller and a current generator; the current
controller is configured to receive the first bleeder control
signal and generate an input voltage based at least in part on the
first bleeder control signal; and the current generator is
configured to receive the rectified voltage and the input voltage
and generate the bleeder current based at least in part on the
input voltage; wherein, if the first bleeder control signal
indicates that the bleeder current is not allowed to be generated:
the current controller is configured to gradually reduce the input
voltage from a first voltage magnitude at a first time to a second
voltage magnitude at a second time; and the current generator is
configured to gradually reduce the bleeder current from a first
current magnitude at the first time to a second current magnitude
at the second time; wherein the second time follows the first time
by a predetermined duration of time. For example, the system is
implemented according to at least FIG. 3, FIG. 6, FIG. 9, and/or
FIG. 12.
[0226] As an example, the current controller includes a switch, an
amplifier, a resistor, and a capacitor; wherein: the capacitor
includes a first capacitor terminal and a second capacitor
terminal, the first capacitor terminal being configured to provide
the input voltage, the second capacitor terminal being biased to a
ground voltage; the resistor includes a first resistor terminal and
a second resistor terminal, the second resistor terminal being
biased to the ground voltage; and the amplifier includes a first
amplifier input terminal, a second amplifier input terminal, and an
amplifier output terminal, the second amplifier input terminal
being connected to the amplifier output terminal, the first
amplifier input terminal being biased to a reference voltage;
wherein: the switch is configured to: receive the first bleeder
control signal; and based at least in part on the first bleeder
control signal, connect the first capacitor terminal to the
amplifier output terminal or to the first resistor terminal; and
the switch is further configured to: if the bleeder current is
allowed to be generated, connect the first capacitor terminal to
the amplifier output terminal to generate the bleeder current based
at least in part on the reference voltage; and if the bleeder
current is not allowed to be generated, connect the first capacitor
terminal to the first resistor terminal to gradually reduce the
bleeder current from the first current magnitude at the first time
to the second current magnitude at the second time.
[0227] For example, the bleeder controller includes a comparator
and a first delayed-signal generator; wherein: the comparator is
configured to receive the sensing signal and a threshold voltage
and generate a comparison signal based at least in part on the
sensing signal and the threshold voltage; and the first
delayed-signal generator is configured to receive the comparison
signal and generate the first bleeder control signal based at least
in part on the comparison signal; wherein the first delayed-signal
generator is further configured to, if the comparison signal
indicates that the sensing signal becomes larger than the threshold
voltage, change the first bleeder control signal from a first logic
level to a second logic level after a first predetermined delay,
the first predetermined delay being larger than zero in magnitude;
wherein: the first logic level indicates that the bleeder current
is allowed to be generated; and the second logic level indicates
that the bleeder current is not allowed to be generated.
[0228] As an example, the bleeder controller is further configured
to generate N bleeder control signals corresponding to N
predetermined delays respectively, N being an integer larger than
1; wherein: the N bleeder control signals include a 1.sup.st
bleeder control signal, . . . , an n.sup.th bleeder control signal,
. . . , and an N.sup.th bleeder control signal, n being an integer
larger than 1 but smaller than N; and the N predetermined delays
include a 1.sup.st predetermined delay, . . . , an n.sup.th
predetermined delay, . . . , and an N.sup.th predetermined delay;
wherein: the 1.sup.st bleeder control signal is the first bleeder
control signal; the 1.sup.st predetermined delay is the first
predetermined delay; and each delay of the N predetermined delays
is larger than zero in magnitude; wherein the bleeder controller is
further configured to: if the (n-1).sup.th bleeder control signal
changes from indicating that the bleeder current is allowed to be
generated to indicating that the bleeder current is not allowed to
be generated, change the n.sup.th bleeder control signal after the
n.sup.th predetermined delay; and if the (N-1).sup.th bleeder
control signal changes from indicating that the bleeder current is
allowed to be generated to indicating that the bleeder current is
not allowed to be generated, change the N.sup.th bleeder control
signal after the N.sup.th predetermined delay.
[0229] For example, the current controller includes N switches, N
amplifiers, a resistor, and a capacitor, the N switches and the N
amplifiers corresponding to N reference voltages; the N switches
include a 1.sup.st switch, . . . , an n.sup.th switch, . . . , and
an N.sup.th switch; the N amplifiers include a 1.sup.st amplifier,
. . . , an n.sup.th amplifier, . . . , and an N.sup.th amplifier;
and the N reference voltages include a 1.sup.st reference voltage,
. . . , an n.sup.th reference voltage, . . . , and an N.sup.th
reference voltage; wherein: the 1.sup.st amplifier includes a
1.sup.st amplifier positive input amplifier, a 1.sup.st amplifier
negative input terminal, and a 1.sup.st amplifier output terminal,
the 1.sup.st amplifier negative input terminal being connected to
the 1.sup.st amplifier output terminal, the 1.sup.st amplifier
positive input amplifier being biased to the 1.sup.st reference
voltage; the n.sup.th amplifier includes an n.sup.th amplifier
positive input terminal, an n.sup.th amplifier negative input
terminal, and an n.sup.th amplifier output terminal, the n.sup.th
amplifier negative input terminal being connected to the n.sup.th
amplifier output terminal; and the N.sup.th amplifier includes an
N.sup.th amplifier positive input terminal, an N.sup.th amplifier
negative input terminal, and an N.sup.th amplifier output terminal,
the N.sup.th amplifier negative input terminal being connected to
the N.sup.th amplifier output terminal; wherein: the capacitor
includes a first capacitor terminal and a second capacitor
terminal, the first capacitor terminal being configured to provide
the input voltage, the second capacitor terminal being biased to a
ground voltage; and the resistor includes a first resistor terminal
and a second resistor terminal, the second resistor terminal being
connected to the 2.sup.nd amplifier output terminal; wherein the
1.sup.st switch is configured to: receive the 1.sup.st bleeder
control signal; and based at least in part on the 1.sup.st bleeder
control signal, connect the first capacitor terminal to the
1.sup.st amplifier output terminal or to the first resistor
terminal; wherein the 1.sup.st switch is further configured to: if
the 1.sup.st bleeder control signal indicates that the bleeder
current is allowed to be generated, connect the first capacitor
terminal to the 1.sup.st amplifier output terminal; and if the
1.sup.st bleeder control signal indicates that the bleeder current
is not allowed to be generated, connect the first capacitor
terminal to the first resistor terminal so that the first capacitor
terminal is connected to the 2.sup.nd amplifier output terminal
through the resistor; wherein the n.sup.th switch is configured to:
receive the n.sup.th bleeder control signal; and based at least in
part on the n.sup.th bleeder control signal, connect the n.sup.th
amplifier positive input terminal to the n.sup.th reference voltage
or to the (n+1).sup.th amplifier output terminal; wherein the
n.sup.th switch is further configured to: if the n.sup.th bleeder
control signal indicates that the bleeder current is allowed to be
generated, connect the n.sup.th amplifier positive input terminal
to the n.sup.th reference voltage; and if the n.sup.th bleeder
control signal indicates that the bleeder current is not allowed to
be generated, connect the n.sup.th amplifier positive input
terminal to the (n+1).sup.th amplifier output terminal; wherein the
N.sup.th switch is configured to: receive the N.sup.th bleeder
control signal; and based at least in part on the N.sup.th bleeder
control signal, connect the N.sup.th amplifier positive input
terminal to the N.sup.th reference voltage or to the ground
voltage; wherein the N.sup.th switch is further configured to: if
the N.sup.th bleeder control signal indicates that the bleeder
current is allowed to be generated, connect the N.sup.th amplifier
positive input terminal to the N.sup.th reference voltage; and if
the N.sup.th bleeder control signal indicates that bleeder current
is not allowed to be generated, connect the N.sup.th amplifier
positive input terminal to the ground voltage; wherein: the
(n-1).sup.th reference voltage is larger than the nth reference
voltage; the n.sup.th reference voltage is larger than the
(n+1).sup.th reference voltage; and the N.sup.th reference voltage
is larger than zero.
[0230] As an example, the bleeder controller further includes N
delayed-signal generators, the N delayed-signal generators
corresponding to the N predetermined delays; and the N
delayed-signal generators include a 1.sup.st delayed-signal
generator, . . . , an n.sup.th delayed-signal generator, . . . ,
and an N.sup.th delayed-signal generator, the 1.sup.st
delayed-signal generator being the first delayed-signal generator;
wherein the first delayed-signal generator is further configured
to, if the comparison signal indicates that the sensing signal
becomes larger than the threshold voltage, change the first bleeder
control signal after the first predetermined delay; wherein the
n.sup.th delayed-signal generator is configured to: receive the
(n-1).sup.th bleeder control signal; generate the n.sup.th bleeder
control signal based at least in part on the (n-1).sup.th bleeder
control signal; and if the (n-1).sup.th bleeder control signal
indicates that the sensing signal becomes larger than the threshold
voltage, change the n.sup.th bleeder control signal after the
n.sup.th predetermined delay; wherein the N.sup.th delayed-signal
generator is configured to: receive the (N-1).sup.th bleeder
control signal; generate the N.sup.th bleeder control signal based
at least in part on the (N-1).sup.th bleeder control signal; and if
the (N-1).sup.th bleeder control signal indicates that the sensing
signal becomes larger than the threshold voltage, change the
N.sup.th bleeder control signal after the N.sup.th predetermined
delay.
[0231] For example, the current regulator includes an amplifier, a
transistor, and a resistor; the transistor includes a gate
terminal, a drain terminal, and a source terminal; the amplifier
includes an amplifier positive input terminal, an amplifier
negative input terminal, and an amplifier output terminal; and the
resistor includes a first resistor terminal and a second resistor
terminal; wherein: the gate terminal is coupled to the amplifier
output terminal; the drain terminal is coupled to the one or more
light emitting diodes; the source terminal is coupled to the first
resistor terminal; the amplifier positive input terminal is biased
to a reference voltage; the amplifier negative input terminal is
coupled to the source terminal; and the second resistor terminal is
biased to a ground voltage; wherein the first resistor terminal is
configured to generate the sensing signal representing the diode
current flowing through the one or more light emitting diodes.
[0232] As an example, the current generator includes an amplifier,
a transistor, and a resistor; the transistor includes a gate
terminal, a drain terminal, and a source terminal; the amplifier
includes an amplifier positive input terminal, an amplifier
negative input terminal, and an amplifier output terminal; and the
resistor includes a first resistor terminal and a second resistor
terminal; wherein: the gate terminal is coupled to the amplifier
output terminal; the drain terminal is biased to the rectified
voltage associated with the TRIAC dimmer and generated by the
rectifying bridge; the source terminal is coupled to the first
resistor terminal; the second resistor terminal is biased to a
ground voltage; the amplifier negative input terminal is coupled to
the source terminal; and the amplifier positive input terminal is
configured to receive the input voltage.
[0233] According to certain embodiments, a system for controlling
one or more light emitting diodes includes: a current regulator
including a first regulator terminal and a second regulator
terminal, the first regulator terminal being configured to receive
a diode current flowing through the one or more light emitting
diodes, the current regulator being configured to generate a
sensing signal representing the diode current, the second regulator
terminal being configured to output the sensing signal; a voltage
divider including a first divider terminal and a second divider
terminal, the first divider terminal being configured to receive a
rectified voltage associated with a TRIAC dimmer and generated by a
rectifying bridge, the voltage divider being configured to generate
a converted voltage proportional to the rectified voltage, the
second divider terminal being configured to output the converted
voltage; a bleeder controller including a first controller
terminal, a second controller terminal and a third controller
terminal, the first controller terminal being configured to receive
the converted voltage from the second divider terminal, the second
controller terminal being configured to receive the sensing signal
from the second regulator terminal, the bleeder controller being
configured to generate a first bleeder control signal based at
least in part on the converted voltage, the third controller
terminal being configured to output the first bleeder control
signal, the first bleeder control signal indicating whether a
bleeder current is allowed or not allowed to be generated; and a
bleeder including a first bleeder terminal and a second bleeder
terminal, the first bleeder terminal being configured to receive
the first bleeder control signal from the third controller
terminal, the second bleeder terminal being configured to receive
the rectified voltage; wherein: the bleeder includes a current
controller and a current generator; the current controller is
configured to receive the first bleeder control signal and generate
an input voltage based at least in part on the first bleeder
control signal; and the current generator is configured to receive
the rectified voltage and the input voltage and generate the
bleeder current based at least in part on the input voltage;
wherein, if the first bleeder control signal indicates that the
bleeder current is not allowed to be generated: the current
controller is configured to gradually reduce the input voltage from
a first voltage magnitude at a first time to a second voltage
magnitude at a second time; and the current generator is configured
to gradually reduce the bleeder current from a first current
magnitude at the first time to a second current magnitude at the
second time; wherein the second time follows the first time by a
predetermined duration of time. For example, the system is
implemented according to at least FIG. 9 and/or FIG. 12.
[0234] As an example, the bleeder controller includes a conduction
phase detector configured to: determine a phase range within which
the TRIAC dimmer is in a conduction state based on at least
information associated with the converted voltage; and generate a
detection signal by comparing the phase range within which the
TRIAC dimmer is in the conduction state and a predetermined
conduction phase threshold; and the bleeder controller is further
configured to: if the phase range within which the TRIAC dimmer is
in the conduction state is determined to be larger than the
predetermined conduction phase threshold, generate the first
bleeder control signal based at least in part on the sensing
signal; and if the phase range within which the TRIAC dimmer is in
the conduction state is determined to be smaller than the
predetermined conduction phase threshold, generate the first
bleeder control signal based at least in part on the converted
voltage.
[0235] For example, the bleeder controller further includes a first
comparator, a second comparator, a switch, and a first
delayed-signal generator; wherein: the first comparator is
configured to receive the converted voltage and a first threshold
voltage and generate a first comparison signal based at least in
part on the converted voltage and the first threshold voltage; and
the second comparator is configured to receive the sensing signal
and a second threshold voltage and generate a second comparison
signal based at least in part on the sensing signal and the second
threshold voltage; wherein the conduction phase detector is further
configured to: receive the first comparison signal; and generate
the detection signal based at least in part on the first comparison
signal; wherein the switch is configured to receive the detection
signal; wherein, if the phase range within which the TRIAC dimmer
is in the conduction state is determined to be smaller than the
predetermined conduction phase threshold: the switch is configured
to output the first comparison signal to the first delayed-signal
generator; and if the first comparison signal indicates that the
converted voltage becomes larger than the first threshold voltage,
change the first bleeder control signal from a first logic level to
a second logic level after a first predetermined delay; wherein, if
the phase range within which the TRIAC dimmer is in the conduction
state is determined to be larger than the predetermined conduction
phase threshold: the switch is configured to output the second
comparison signal to the first delayed-signal generator; and if the
second comparison signal indicates that the sensing signal becomes
larger than the second threshold voltage, change the first bleeder
control signal from the first logic level to the second logic level
after the first predetermined delay; wherein: the first
predetermined delay is larger than zero in magnitude; the first
logic level indicates that the bleeder current is allowed to be
generated; and the second logic level indicates that the bleeder
current is not allowed to be generated.
[0236] As an example, the conduction phase detector includes a
duration determination device and a phase detection device;
wherein: the duration determination device is configured to receive
the first comparison signal, determine a time duration during which
the first comparison signal indicates the converted voltage is
smaller than the first threshold voltage, and output a timing
signal representing the time duration; and the phase detection
device is configured to receive the timing signal representing the
time duration, compare the time duration and a duration threshold,
and generate the detection signal based at least in part on the
time duration and the duration threshold, the detection signal
indicating whether the time duration is larger than the duration
threshold; wherein: if the detection signal indicates that the time
duration is larger than the duration threshold, the phase range
within which the TRIAC dimmer is in the conduction state is
determined to be smaller than the predetermined conduction phase
threshold; and if the detection signal indicates that the time
duration is smaller than the duration threshold, the phase range
within which the TRIAC dimmer is in the conduction state is
determined to be larger than the predetermined conduction phase
threshold.
[0237] For example, the bleeder controller is configured to
generate N bleeder control signals corresponding to N predetermined
delays respectively, N being an integer larger than 1; wherein: the
N bleeder control signals include a 1.sup.st bleeder control
signal, . . . , an n.sup.th bleeder control signal, . . . , and an
N.sup.th bleeder control signal, n being an integer larger than 1
but smaller than N; and the N predetermined delays include a
1.sup.st predetermined delay, . . . , an n.sup.th predetermined
delay, . . . , and an N.sup.th predetermined delay, each
predetermined delay of the N predetermined delays being larger than
zero in magnitude; wherein: the 1.sup.st bleeder control signal is
the first bleeder control signal; and the 1.sup.st predetermined
delay is the first predetermined delay; wherein the bleeder
controller is further configured to: if the (n-1).sup.th bleeder
control signal changes from indicating that the bleeder current is
allowed to be generated to indicating that the bleeder current is
not allowed to be generated, change the n.sup.th bleeder control
signal after the n.sup.th predetermined delay; and if the
(N-1).sup.th bleeder control signal changes from indicating that
the bleeder current is allowed to be generated to indicating that
the bleeder current is not allowed to be generated, change the
N.sup.th bleeder control signal after the N.sup.th predetermined
delay.
[0238] As an example, the bleeder controller further includes N
delayed-signal generators; and the N delayed-signal generators
include a 1.sup.st delayed-signal generator, . . . , an n.sup.th
delayed-signal generator, . . . , and an N.sup.th delayed-signal
generator; wherein the 1.sup.st delayed-signal generator is the
first delayed-signal generator.
[0239] According to some embodiments, a system for controlling one
or more light emitting diodes includes: a current regulator
including a first regulator terminal and a second regulator
terminal, the first regulator terminal being configured to receive
a diode current flowing through the one or more light emitting
diodes, the current regulator being configured to generate a
sensing signal representing the diode current, the second regulator
terminal being configured to output the sensing signal; a voltage
divider including a first divider terminal and a second divider
terminal, the first divider terminal being configured to receive a
rectified voltage associated with a TRIAC dimmer and generated by a
rectifying bridge, the voltage divider being configured to generate
a converted voltage proportional to the rectified voltage, the
second divider terminal being configured to output the converted
voltage; a bleeder controller including a first controller
terminal, a second controller terminal and a third controller
terminal, the first controller terminal being configured to receive
the converted voltage from the second divider terminal, the second
controller terminal being configured to receive the sensing signal
from the second regulator terminal, the bleeder controller being
configured to generate a first bleeder control signal based at
least in part on the converted voltage, the third controller
terminal being configured to output the first bleeder control
signal, the first bleeder control signal indicating whether a
bleeder current is allowed or not allowed to be generated; and a
bleeder including a first bleeder terminal and a second bleeder
terminal, the first bleeder terminal being configured to receive
the first bleeder control signal from the third controller
terminal, the second bleeder terminal being configured to receive
the rectified voltage, the bleeder being configured to generate the
bleeder current based at least in part on the first bleeder control
signal; wherein the bleeder controller is configured to: determine
a phase range within which the TRIAC dimmer is in a conduction
state based on at least information associated with the converted
voltage; and generate a detection signal by comparing a
predetermined conduction phase threshold and the phase range within
which the TRIAC dimmer is in the conduction state; wherein the
bleeder controller is further configured to: if the detection
signal indicates that the phase range within which the TRIAC dimmer
is in the conduction state is larger than the predetermined
conduction phase threshold, generate the first bleeder control
signal based at least in part on the sensing signal; and if the
detection signal indicates that the phase range within which the
TRIAC dimmer is in the conduction state is determined to be smaller
than the predetermined conduction phase threshold, generate the
first bleeder control signal based at least in part on the
converted voltage; wherein: if the first bleeder control signal
indicates that the bleeder current is not allowed to be generated,
the current generator is configured to gradually reduce the bleeder
current from a first current magnitude at a first time to a second
current magnitude at a second time; wherein the second time follows
the first time by a predetermined duration of time. For example,
the system is implemented according to at least FIG. 9 and/or FIG.
12.
[0240] As an example, the bleeder controller further includes a
delayed-signal generator; wherein: the delayed-signal generator is
configured to change the first bleeder control signal from a first
logic level to a second logic level after a predetermined delay,
the predetermined delay being larger than zero in magnitude; the
first logic level indicates that the bleeder current is allowed to
be generated; and the second logic level indicates that the bleeder
current is not allowed to be generated.
[0241] For example, the bleeder controller further includes N
delayed-signal generators, the N delayed-signal generators being
configured to generate N bleeder control signals corresponding to N
predetermined delays respectively, N being an integer larger than
1; and the bleeder is configured to receive the N bleeder control
signals; wherein: the N delayed-signal generators include a
1.sup.st delayed-signal generator, . . . , an n.sup.th
delayed-signal generator, . . . , and an N.sup.th delayed-signal
generator, n being an integer larger than 1 but smaller than N; the
N bleeder control signals include a 1.sup.st bleeder control
signal, . . . , an n.sup.th bleeder control signal, . . . , and an
N.sup.th bleeder control signal, the 1.sup.st bleeder control
signal being the first bleeder control signal; and the N
predetermined delays include a 1.sup.st predetermined delay, . . .
, an n.sup.th predetermined delay, . . . , and an N.sup.th
predetermined delay, each predetermined delay of the N
predetermined delays being larger than zero in magnitude; wherein
the n.sup.th delayed-signal generator is configured to receive the
(n-1).sup.th bleeder control signal and change the n.sup.th bleeder
control signal after the n.sup.th predetermined delay if the
(n-1).sup.th bleeder control signal indicates a change from the
bleeder current being allowed to be generated to the bleeder
current not being allowed to be generated; wherein, the bleeder is
further configured to, if the bleeder current changes from being
allowed to be generated to not being allowed to be generated,
reduce the bleeder current from a 1.sup.st predetermined magnitude
to a 2.sup.nd predetermined magnitude during a predetermined
duration of time in response to at least a change of the 1.sup.st
bleeder control signal; reduce the bleeder current from an n.sup.th
predetermined magnitude to an (n+1).sup.th predetermined magnitude
during the predetermined duration of time in response to at least a
change of the n.sup.th bleeder control signal; and reduce the
bleeder current from an N.sup.th predetermined magnitude to zero
during the predetermined duration of time in response to at least a
change of the N.sup.th bleeder control signal; wherein: the
(n-1).sup.th predetermined magnitude is larger than the n.sup.th
predetermined magnitude; the nth predetermined magnitude is larger
than the (n+1).sup.th predetermined magnitude; and the N.sup.th
predetermined magnitude is larger than zero.
[0242] According to certain embodiments, a method for controlling
one or more light emitting diodes includes: receiving a diode
current flowing through the one or more light emitting diodes;
generating a sensing signal representing the diode current;
outputting the sensing signal; receiving the sensing signal;
generating a first bleeder control signal based at least in part on
the sensing signal, the first bleeder control signal indicating
whether a bleeder current is allowed or not allowed to be
generated; outputting the first bleeder control signal; receiving
the first bleeder control signal; generating an input voltage based
at least in part on the first bleeder control signal; receiving the
input voltage and a rectified voltage associated with a TRIAC
dimmer; generating the bleeder current based at least in part on
the input voltage; wherein: the generating an input voltage based
at least in part on the first bleeder control signal includes, if
the first bleeder control signal indicates that the bleeder current
is not allowed to be generated, gradually reducing the input
voltage from a first voltage magnitude at a first time to a second
voltage magnitude at a second time; and the generating the bleeder
current based at least in part on the input voltage includes, if
the first bleeder control signal indicates that the bleeder current
is not allowed to be generated, gradually reducing the bleeder
current from a first current magnitude at the first time to a
second current magnitude at the second time; wherein the second
time follows the first time by a predetermined duration of time.
For example, the method is implemented according to at least FIG.
3, FIG. 6, FIG. 9, and/or FIG. 12.
[0243] According to some embodiments, a method for controlling one
or more light emitting diodes includes: receiving a diode current
flowing through the one or more light emitting diodes; generating a
sensing signal representing the diode current; outputting the
sensing signal; receiving a rectified voltage associated with a
TRIAC dimmer; generating a converted voltage proportional to the
rectified voltage; outputting the converted voltage; receiving the
converted voltage and the sensing signal; generating a first
bleeder control signal based at least in part on the converted
voltage, the first bleeder control signal indicating whether a
bleeder current is allowed or not allowed to be generated;
outputting the first bleeder control signal; receiving the first
bleeder control signal; generating an input voltage based at least
in part on the first bleeder control signal; receiving the input
voltage and the rectified voltage; and generating the bleeder
current based at least in part on the input voltage; wherein: the
generating an input voltage based at least in part on the first
bleeder control signal includes, if the first bleeder control
signal indicates that the bleeder current is not allowed to be
generated, gradually reducing the input voltage from a first
voltage magnitude at a first time to a second voltage magnitude at
a second time; and the generating the bleeder current based at
least in part on the input voltage includes, if the first bleeder
control signal indicates that the bleeder current is not allowed to
be generated, gradually reducing the bleeder current from a first
current magnitude at the first time to a second current magnitude
at the second time; wherein the second time follows the first time
by a predetermined duration of time. For example, the method is
implemented according to at least FIG. 9 and/or FIG. 12.
[0244] According to certain embodiments, a method for controlling
one or more light emitting diodes, the method comprising: receiving
a diode current flowing through the one or more light emitting
diodes; generating a sensing signal representing the diode current;
outputting the sensing signal; receiving a rectified voltage
associated with a TRIAC dimmer; generating a converted voltage
proportional to the rectified voltage; outputting the converted
voltage; receive the converted voltage and the sensing signal;
generating a first bleeder control signal based at least in part on
the converted voltage, the first bleeder control signal indicating
whether a bleeder current is allowed or not allowed to be
generated; outputting the first bleeder control signal; receiving
the first bleeder control signal and the rectified voltage; and
generating the bleeder current based at least in part on the input
voltage; wherein the generating a first bleeder control signal
based at least in part on the converted voltage includes:
determining a phase range within which the TRIAC dimmer is in a
conduction state based on at least information associated with the
converted voltage; generating a detection signal by comparing a
predetermined conduction phase threshold and the phase range within
which the TRIAC dimmer is in the conduction state; if the detection
signal indicates that the phase range within which the TRIAC dimmer
is in the conduction state is larger than the predetermined
conduction phase threshold, generating the first bleeder control
signal based at least in part on the sensing signal; and if the
detection signal indicates that the phase range within which the
TRIAC dimmer is in the conduction state is smaller than the
predetermined conduction phase threshold, generating the first
bleeder control signal based at least in part on the converted
voltage; wherein the generating the bleeder current based at least
in part on the input voltage includes, if the first bleeder control
signal indicates that the bleeder current is not allowed to be
generated, gradually reducing the bleeder current from a first
current magnitude at a first time to a second current magnitude at
a second time; wherein the second time follows the first time by a
predetermined duration of time. For example, the method is
implemented according to at least FIG. 9 and/or FIG. 12.
[0245] For example, some or all components of various embodiments
of the present invention each are, individually and/or in
combination with at least another component, implemented using one
or more software components, one or more hardware components,
and/or one or more combinations of software and hardware
components. As an example, some or all components of various
embodiments of the present invention each are, individually and/or
in combination with at least another component, implemented in one
or more circuits, such as one or more analog circuits and/or one or
more digital circuits. For example, various embodiments and/or
examples of the present invention can be combined.
[0246] Although specific embodiments of the present invention have
been described, it will be understood by those of skill in the art
that there are other embodiments that are equivalent to the
described embodiments. Accordingly, it is to be understood that the
invention is not to be limited by the specific illustrated
embodiments.
* * * * *